Darshan Institute of Engineering & Technology for Diploma Studies Unit 2

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1 Intrductin Oracle prgramming language SQL, prvides varius functinalities required t manage a database. SQL is s much pwerful in handling data and varius database bjects. But it lacks sme f basic functinalities prvided by ther prgramming language. Fr example, SQL des nt prvide basic prcedural capabilities such as cnditinal checking, branching and lping. In SQL, it is nt pssible t cntrl executin f SQL statements based n sme cnditin r user inputs. Oracle prvides PLSQL (Prcedural Language Structured Query Language) t vercme disadvantages f SQL. PLSQL is super set f SQL. PLSQL supprts all the functinalities prvided by SQL alng with its wn prcedural capabilities. Any SQL statements can be used in PLSQL prgram with n change, except SQL s data definitin statements such as CREATE TABLE. Data definitin statements are nt allwed because PLSQL cde is cmpile time. S, it cannt refer t bjects that d nt yet exist. Advantages f PLSQL Advantages f PLSQL are describe belw: 1) Prcedural Capabilities: PLSQL prvides prcedural capabilities such as cnditin checking, branching and lping. This enables prgrammer t cntrl executin f a prgram based n sme cnditins and user inputs. 2) Supprt t variables: PLSQL supprts declaratin and use f variables. These variables can be used t stre intermediate results f a query r sme expressin. 3) Errr Handling: When an errr ccurs, user friendly message can be displayed. Als, executin f prgram can be cntrlled instead f abruptly terminating the prgram. 4) User Defined Functins: Alng with a large set f in-build functins, PLSQL als supprts user defined functins and prcedures. 5) Prtability: Prgrams written in PLSQL are prtable. It means, prgrams can be transferred and executed frm any ther cmputer hardware and perating system, where Oracle is peratinal. 6) Sharing f Cde: PLSQL allws user t stre cmpiled cde in database. This cde can be accessed and shared by different applicatins. This cde can be executed by ther prgramming language like JAVA. 1

2 7) Efficient Executin: PLSQL sends an entire blck f SQL statements t the Oracle engine, where these statements are executed in ne g. This reduces netwrk traffic and imprves efficiency f executin. In case f SQL, all statements are transferred ne by ne. The Generic PLSQL Blck PLSQL cde is gruped int structures called blck. A blck is called a named blck, if it is given particular name t identify. A blck is called an annymus blck, if it is nt given any name. Named blcks are created while creating database bjects such as functin, prcedure, package and trigger. The structure f a typical PLSQL blck can be given as belw: DECLARE -- Optinal <Declaratin Sectin> -- Mandatry <Executable Cmmands> EXCEPTION -- Optinal <Exceptin Handling> END ; -- Mandatry Ntice that DECLARE and EXCEPTION are ptinal while and END are mandatry. Als, ; at the end t terminate the blck. A blck f PLSQL cde cntains three sectins given as belw: 1) Declaratins 2) Executable Cmmands 3) Exceptin Handling 1) Declaratins: This sectin starts with the keywrd DECLARE. It defines and initializes variables and cursrs used in the blck. This sectin is ptinal sectin. If blck des nt require any variables r cursrs then this sectin can be mitted frm the blck. 2) Executable Cmmands: This sectin starts with the keywrd. This is the nly mandatry sectin in the PLSQL blck. It cntains varius SQL and PLSQL statements prviding functinalities like data retrieval, manipulatin, lping and branching. 3) Exceptin Handling: This sectin starts with the keywrd EXCEPTION. This sectin handles errrs that arise during the executin f data manipulatin statements in executable cmmands sectin. This sectin is ptinal sectin. If blck des nt handle any exceptin explicitly then this sectin can be mitted frm the blck. 2

3 Data Types PLSQL is super set f the SQL. S, it supprts all the data types prvided by SQL. Alng with this, in PLSQL Oracle prvides subtypes f the data types. Fr example, the data type NUMBER has a subtype called INTEGER. These subtypes can be used in PLSQL blck t make the data type cmpatible with the data types f the ther prgramming languages. The varius data types can be given as belw: Categry Data Type Sub typesvalues Numerical NUMBER BINARY_INTEGER, DEC, DECIMAL, DOUBLE PRECISION, FLOAT, INTEGER, INT, NATURAL, POSITIVE, REAL, SMALLINT Character CHAR, LONG, VARCHAR2 CHARACTER,VARCHAR, STRING, NCHAR, NVARCHAR2 Date DATE Binary RAW, LONG RAW Blean BOOLEAN Can have value like TRUE, FALSE and NULL. RwID ROWID Stres values f address f each recrd. Variables Variables are used t stre values that may be change during the executin f prgram. In PLSQL, variables cntain values resulting frm queries r expressin. Variables are declared in Declaratin sectin f the PLSQL blck. It must be assign valid data type and can als be initialized if necessary. Declaring a Variable variablename datatype [ NOT NULL] := initialvalue; datatype can be any valid data type supprted by PLSQL. := used fr assignment peratin. If variable need t be initialized then initialvalue can be assigned at declaratin time. If NOT NULL is included in declaratin, variable cannt have NULL value during prgram executin and such variable must be initialized. Example 1 : Sme f the valid variable declaratin are given belw: n NUMBER(3); value DECIMAL; city CHAR(10); name VARCHAR(10); cunter NUMBER(2) NOT NULL := 0 Anchred Data Type A variable can be declared as having anchred data type. It means, datatype fr variable is determined based n the data type f the ther bject. This bject can be ther variable r a clumn f the table. This prvides ability t match the data types f the variables with the data types f the clumns defined in the database. If data type f clumn is changed, then the data type f variable will als changed autmatically. 3

4 Advantage: This reduces maintenance cst and allw a prgram t adapt changes made in tables. variablename bject%type [ NOT NULL ] := initialvalue ; bject can be any variable declared previusly r clumn f a database. T refer f a clumn f particular table, clumn name must be cmbined with table name, as describe in belw example. Example 2 : Sme f the valid anchred variable declaratin. n Accunt.Acc_N%TYPE; bal Accunt.Balance%TYPE; name Custmer.name%TYPE; Declaring a Cnstant A cnstant is als used t stre value like a variable. But, unlike variable, a value stred in cnstant cannt be changed during prgram executin. cnstantname CONSTANT datatype := initialvalue ; A cnstant must be initialized at declaratin time. Fr example, fllwing statement declared a cnstant named pi. pi CONSTANT NUMBER(3,2) := 3.14 ; Assigning a Value There are three ways t assign value t a variable as given belw: 1) By using Assignment Operatr: variablename := value ; A value can be a cnstant value r result f sme expressin r return value f sme functin. 2) By Reading frm the Keywrd: variablename := &variablename ; This is similar t scanf() functin. Whenever & is encuntered, a value read frm the keybard and assign it t variable. Fr example, fllwing statement assigns value read frm the keybard t variable n. n := &n; 3) Selecting r Fetching table data values int Variables: SELECT cl1, cl2,, cln INTO var1, var2,, varn FROM tablename WHERE cnditin ; This statement retrieves values fr specified clumn and stres them in given variable. Data type and size f variables must be cmpatible with the relative clumns. A cnditin in WHERE clause must be such that it selects nly single recrd. This statement cannt wrk if multiple recrds are selected. 4

5 Example 3 : Fllwing PLSQL blck stres accunt number and balance fr accunt A01 int variable n and bal. DECLARE n Accunt.Acc_N%TYPE; bal Accunt.Balance%TYPE; END; Displaying Messages SELECT Acc_N, Balance INTO n, bal FROM Accunt WHERE Acc_N = A01 ; T display messages r any utput n the screen in PLSQL, fllwing statement is used. dbms_utput.put_line ( message ); A dbms_utput is a package, which prvides functins t accumulate infrmatin in a buffer. A put_line is a functin, which display messages n the screen. A message is a character string t be displayed. T display data f ther data type, they must be cncatenated with sme character string. The envirnment parameter, - SERVEROUTPUT - must be ON t display messages n screen. Example 4 : Fllwing statements display varius utputs n the screen. dbms_utput.put_line ( Hi Hell Wrld ); Hi Hell Wrld dbms_utput.put_line ( Sum = 25 ); Sum = 25 dbms_utput.put_line ( PI = pi ); PI = 3.14 dbms_utput.put_line ( Square f 3 is 9 ); Square f 3 is 9 Cmments Cmments are statement that will nt get executed even thugh they are present in the prgram cde. Cmments are used t increase readability f a prgram. In PLSQL, a cmment has tw frms: 1) -- (Duble hyphen r duble dash) (Single Line Cmment): Treats single line as a cmment. -- This single line is a cmment. 2) *. * (Multiple Line Cmment): Treats multiple lines as cmment. * This statement is spread ver tw line and bth lines are treated as cmments * 5

6 Creating and Executing a PLSQL Blck T create and execute a PLSQL blck, fllw the steps given belw: Open any editr like as ntepad. An EDIT cmmand can be used n SQL prmpt t pen a ntepad frm the SQL * PLUS envirnment. The fllwing syntax creates and pens a file: EDIT filename Example: EDIT D:PLSQLtest.sql Create and pen a file named test.sql. Write a prgram cde r statements in a file and save it. File shuld have.sql extensin and last statement in file shuld be. T execute this blck, use any f the fllwing cmmands n prmpt. RUN filename START filename filename Cntrl Structures Example: Fllwing cmmand executes a blck saved in file test.sql D:PLSQLtest.sql In PLSQL, the flw f executin can be cntrlled in three different manners as given belw: 1) Cnditinal Cntrl 2) Iterative Cntrl 3) Sequential Cntrl Fr varius example, Accunt table that is given belw is used: Accunt Acc_N Balance B_Name A Rjt A Ahmd A Srt A Brd 1) Cnditinal Cntrl: T cntrl the executin f blck f cde based n sme cnditin, PLSQL prvides the IF statement. The IF THEN ELSEIF ELSE END IF cnstruct can be used t execute specific part f the blck based n the cnditin prvided. IF cnditin THEN -- Execute cmmands ELSE IF cnditin THEN -- Execute cmmand. 6

7 . ELSE -- Execute cmmand END IF; Example 5 : Write a prgram t read a number frm user and determine whether it is dd r even. DECLARE n NUMBER; -- declare a variable t stre number -- read a number frm the user. dbms_utput.put_line ( Enter value fr n: ); n := &n; -- Check result f MOD functin IF MOD (n, 2) = 0 THEN dbms_utput.put_line ( Given Number n is EVEN. ); ELSE dbms_utput.put_line ( Given Number n is ODD. ); END IF ; END ; Output: Enter value fr n: 7 Old 5: n := &n; New 5: n := 7; Given Number 7 is ODD. Observe the utput. A message is displayed autmatically t enter value fr variable suffixed with &. It is als displays the ld and new values fr that variable. And at the end final message is displayed, whether number is even r dd. Als d nt frget t set SERVEROUTPUT n. Example 6 : Write a prgram t debit a given accunt. Read accunt number and amunt t be debited. Debit the balance if the resulting balance is nt less than zer. This means, a balance in accunt shuld nt g t negative while withdrawing amunt. DECLARE -- declare required variables n Accunt.Acc_N%TYPE; bal Accunt.Balance%TYPE; newbalance Accunt.Balance%TYPE; amunt NUMBER(7,2); -- read accunt number and amunt t be debited n := &n; amunt := &amunt; 7

8 Output 1 : Output 2 : END ; -- retrieve the current balance fr given accunt SELECT Balance INTO bal FROM Accunt Where Acc_N = n ; -- calculate a new balance newbalance := bal amunt ; -- Update balance if new balance zer r psitive IF newbalance >= 0 THEN UPDATE Accunt SET Balance = newbalance WHERE Acc_N = n ; dbms_utput.put_line( Accunt Debited Successfully.. ); ELSE dbms_utput.put_line( Nt Sufficient Balance.. ); END IF ; Enter value fr n : A01 Enter value fr amunt : 3000 Nt Sufficient balance.. PLSQL prcedure successfully cmpleted. Enter value fr n : A03 Enter value fr amunt : 2000 Accunt Debited Successfully.. PLSQL prcedure successfully cmpleted. 2) Iterative Cntrl: Iterative cntrl allws a grup f statements t execute repeatedly in a prgram. It is called Lping. PLSQL prvides three cnstructs t implement lps, as listed belw: 1. LOOP 2. WHILE 3. FOR In PLSQL, any lp starts with a LOOP keywrd and it terminates with an END LOOP keywrd. Each lp requires a cnditinal statement t cntrl the number f times a lp is executed. 1. LOOP LOOP -- Execute cmmands.. END LOOP LOOP is an infinite lp. It executes cmmands in its bdy infinite times. S, it requires an EXIT statement within its bdy t terminate the lp after executing specific iteratin. 8

9 Example 7 : Display number frm 1 t 5 alng with their square values using LOOP cnstruct. DECLARE -- declare required variable cunter NUMBER(3) := 1 ; -- display headers fr utput END ; Output: Value dbms_utput.put_line ( Value Square ); -- Traverse lp LOOP EXIT WHEN cunter > 5; dbms_utput.put_line ( cunter cunter*cunter); cunter := cunter + 1; END LOOP; Square PLSQL prcedure successfully cmpleted. Instead f using EXIT WHEN cunter > 5; we can als use fllwing IF.. END IF blck. IF cunter > 5 THEN EXIT; END IF; 2. WHILE WHILE Cnditin LOOP -- Execute Cmmands.. END LOOP; The WHILE lp executes cmmands in its bdy as lng as the cnditin remains TRUE. The lp terminates when the cnditin evaluates t FALSE r NULL. The EXIT statement can als be used t exit the lp. Example 8 : Display numbers frm 1 t 5 alng with their square values using WHILE cnstruct. DECLARE -- declare required variable cunter NUMBER(3) := 1; -- display headers fr utput dbms_utput.put_line ( Value Square ); -- traverse lp WHILE cunter <= 5 9

10 LOOP dbms_utput.put_line ( cunter cunter*cunter); cunter := cunter + 1; END LOOP; END; Output: Same as previus example FOR FOR variable IN [ REVERSE ] start end LOOP -- Execute cmmand END LOOP Here, a variable is a lp cntrl variable. It is declared implicitly by PLSQL. S, it shuld nt be declared explicitly. The FOR LOOP variable is always incremented by 1 and any ther increment value cannt be specified. A start and end specifies the lwer and upper bund fr the lp cntrl variable. If REVERSE keywrd is prvided, lp is executed in reverse rder (Frm end t start). Example 9 : Display numbers frm 1 t 5 alng with their square values using FOR cnstruct. DECLARE -- declare required variable cunter NUMBER(3) := 1; -- display header fr utput dbms_utput.put_line ( Value Square ); -- traverse lp FOR cunter IN 1 5 LOOP dbms_utput.put_line ( cunter cunter*cunter); END LOOP; END; Output: Same as previus example 7. 3) Sequential Cntrl Nrmally, executin prceeds sequentially within the blck f cde. Sequence can be changed cnditinally as well as uncnditinally. T alter the sequence uncnditinally, the GOTO statement can be used. GOTO : jumphere; 10

11 : << jumphere >> The GOTO statement makes flw f executin t jump at << jumphere >>. The jump is uncnditinal. Example 10 : The fllwing cde illustrates the use f the GOTO statement. dbms_utput.put_line ( Cde Starts. ); dbms_utput.put_line ( Befre GOTO statement.. ); Output: END; GOTO jump; dbms_utput.put_line ( This statement will nt get executed.. ); << jump >> dbms_utput.put_line ( Flw f executin jumped here.. ); Cde Starts. Befre GOTO Statement.. Flw f executin jumped here.. Here, third put_line statement did nt execute. Because GOTO statement, which made the flw f executin t jump at << jump >> and executed frth put_line statement. Transactinal Cntrl Transactinal cntrl cmmands such as COMMIT, ROLLBACK and SAVEPOINT can als be used with PLSQL cde blck t cntrl the transactin. Example 11 : Debit the given accunt with specified amunt. If resultant balance is negative, rllback the peratin. Else, cmmit the transactin. DECLARE -- declare required variables n Accunt.Acc_N%TYPE; bal Accunt.Balance%TYPE; amunt NUMBER(7,2); -- read accunt number and amunt t be debited n := &n; amunt := &amunt; -- create savepint SAVEPOINT negativebalance; -- update balance UPDATE Accunt SET Balance = Balance amunt WHERE Acc_N = n; -- read the new balance SELECT Balance INTO bal FROM Accunt WHERE Acc_N = n; -- display updated balance dbms_utput.put_line( Updated balance is bal ); 11

12 END ; -- if balance is negative then und the debit peratin IF bal < 0 THEN dbms_utput.put_line( Debit peratin rllback. ); ROLLBACK TO SAVEPOINT negativebalance; ELSE dbms_utput.put_line( Debit peratin Cmmitted. ); COMMIT; END IF ; Abve given prgram reads an accunt number and amunt t be debited frm the user. Befre updating the balance, a savepint is created. Once a balance is updated, new balance is retrieved and checked. If it is negative, update peratin is rllback therwise the change is saved permanently using COMMIT. 12

13 Cursr makes pssible t prcess multiple recrds individually. Exceptin Handling prevents quick prgram terminatin, due t run-time errrs and display userfriendly errr messages. PLSQL prvides sme ther database bjects such as prcedures, functins, packages and triggers. PLSQL supprts all the in-built functins f SQL, alng with these PLSQL als allws t create user defined functins and prcedures. Prcedures are almst same as functin except sme basic difference. Prcedures and functins can be gruped tgether int anther bject called package. Package prvides mdularity in develping prgrams fr cmplex systems. Triggers are used t implement business rules which were nt pssible by using CHECK cnstraint r user defined exceptin. Prcedures and Functins A prcedure r functin is a grup f PLSQL statements that perfrms specific task. A prcedure and functin is a named PLSQL blck f cde. This blck can be cmpiled and successfully cmpiled blck can be stred in Oracle database. This prcedure and functin is called Stres Prcedure r Functin. We can pass parameters t prcedures and functins. S that their executin can be changed dynamically. Difference between Prcedures and Functins are given belw: Functins Prcedures A functin must return a value. A prcedure may r may nt return a value. A functin can return nly ne value. A prcedure can return multiple values. A functin can be used with SELECT statement, like in-built SQL functins. A functin cannt directly execute using EXEC cmmand. A prcedure cannt be used with SELECT statement. A prcedure can directly execute using EXEC cmmand. Advantages f prcedures and functins: 1) Security: We can imprve security by giving rights (privilege) t selected persn t execute prcedures and functins. 2) Faster Executin: Cde f prcedures and functins are already cmpiled and n need t cmpile it at run time. S, require less time t execute. 3) Sharing f cde: Once prcedure is created and stred, it can be used by mre than ne user. This requires allcating memry t stre cde nly nce rather than allcating memry fr multiple cpies. This utilized memry efficiently. 4) Prductivity: Cde written in prcedure is shared by all prgrammers. This eliminates redundant cding by multiple prgrammers s verall imprvement in prductivity. 13

14 5) Integrity: A prcedure r functin needs t be tested nly nce t verify its wrking. After this, Oracle is respnsible t maintain its integrity. Example: If tables is altered r destryed, fr which prcedure is created. Oracle autmatically makes this prcedure r functin invalid. Structure f a Prcedure and Functin A prcedure and functin has three sectin as describe belw: 1) Declaratin: This sectin defines variable, cnstants, cursrs, exceptin and ther prcedure and functin. These bjects are lcal t prcedure r functin and they becme invalid nce the prcedure r functin exits. 2) Executable Cmmands: This sectin cntains SQL and PLSQL statements that perfrm a specific task assign t prcedure r functin. Parameter passed t prcedures r functins are utilized here. Data is return back t the calling functin r prcedure frm this sectin. 3) Exceptin Handling: This sectin cntains cde that deals with exceptins generate during the executin f cde. Creating a Prcedure CREATE [OR REPLACE] PROCEDURE prc_name (argument [IN, OUT, IN OUT] datatype) IS Declaratin sectin Executin sectin EXCEPTION Exceptin sectin END ; While declaring a lcal variable, size cannt be specified. Only datatype needs t be specified f a variable. When this prcedure is executed first time, the cde will be cmpiled. If there is n errr then a prcedure is created and stred in racle database. Explanatin: 1) CREATE: It will create a prcedure. 2) REPLACE: It will re create a prcedure if it already exists.if it re-created then racle recmpile it autmatically. 3) We can pass parameters t the prcedures in three ways: 1. IN parameters: These types f parameters are used t send values t stred prcedures. 2. OUT parameters: These types f parameters are used t get values frm stred prcedures. This is similar t a return type in functins but prcedure can return values fr mre than ne parameters. 3. IN OUT parameters: This type f parameter allws us t pass values int a prcedure and get utput values frm the prcedure. 14

15 4) IS : It indicates the beginning f the bdy f the prcedure. The cde between IS and frms the Declaratin sectin. 5) : It cntains the executable statement. 6) Exceptin: It cntains exceptin handling part. This sectin is ptinal. 7) END: It will end the prcedure. By using CREATE OR REPLACE tgether the prcedure is created if it des nt exist and if it exists then it is replaced with the current cde. Executing a Prcedure There are tw ways t execute a prcedure: 1) Frm the SQL prmpt: EXECUTE [r EXEC] prcedure_name (parameter) ; 2) T execute prcedure frm PLSQL blck. OR Within anther prcedure simply use the prcedure name. prcedure_name (parameter) ; A stre prcedure cannt be used with SELECT statement. Example: (Using IN ) CREATE OR REPLACE PROCEDURE get_studentname_by_id (id IN NUMBER) IS SELECT studentname FROM stu_tbl WHERE studentid = id ; END; Execute: EXECUTE get_studentname_by_id (10) ; OR get_studentname_by_id (10) ; Explanatin: Abve prcedure gives the name f student whse id is 10. Example 12 : Create a prcedure debitacc which debit a given accunt with specified amunt. CREATE OR REPLACE PROCEDURE debitacc (n IN Accunt.Acc_N%TYPE, amunt IN NUMBER) IS --declare lcal variable bal Accunt.Balance%TYPE ; newbalance Accunt.Balance%TYPE ; --Retrieve current balance fr given accunt SELECT Balance INTO bal FROM Accunt WHERE Acc_N = n ; -- calculate balance newbalance := bal - amunt ; -- update balance withut wrrying fr negative balance UPDATE Accunt SET balance = newbalance WHERE Acc_N = n ; -- display cnfirmatin message dbms_utput.put_line( Accunt n debited.. ); 15

16 END ; Output: Prcedure created. Execute: debitacc ( A01, 1000) ; OR EXEC debitacc ( A01, 1000) ; If any errr encuntered during cmpilatin, t display errr fllwing statement can be used: SELECT * FROM user_errr; Creating a Functin CREATE [OR REPLACE] FUNCTION func_name (argument IN datatype ) RETURN datatype IS Declaratin sectin Executin sectin EXCEPTION Exceptin sectin END ; While declaring a lcal variable, size cannt be specified. Only datatype needs t be specified f a variable. When this functin is executed first time, the cde will be cmpiled. If there is n errr then a functin is created and stred in racle database. A functin must return ne value back t calling envirnment. It cannt return mre than ne value like prcedure. Explanatin: 1) CREATE: It will create a functin. 2) REPLACE: It will re create a functin if it already exists. If it re-created then racle recmpile it autmatically. 3) IN parameters: These types f parameters are used t send values t stred Functins. 4) RETURN: Functin return value having data type datatype. Executing a Functin There are tw ways t execute a prcedure: 1) Frm the SQL prmpt it shuld be used with SELECT statement. SELECT functin_name (parameter) FROM dual ; 2) T execute functin frm the PLSQL blck. fuctin_name (parameters) ; A stred functin cannt be executed using EXCE cmmand like prcedures. 16

17 Example 13 : Create a functin getbalance which the balance fr the given accunt. CREATE OR REPLACE FUNCTION getbalance (n IN Accunt.Acc_N%TYPE ) RETURN NUMBER Output: Execute: IS END ; --declare lcal variable bal Accunt.Balance%TYPE ; --Retrieve current balance fr given accunt SELECT Balance INTO bal FROM Accunt WHERE Acc_N = n ; -- Return balance RETURN bal ; Functin Created. getbalance ( A03 ) ; OR SELECT getbalance ( A03 ) FROM dual ; Destrying Prcedure and Functin T destry a stred prcedure: DROP PROCEDURE prcedurename ; Example: DROP PROCEDURE debitacc ; Output: Prcedure drpped. T destry a stred functin: DROP FUNCTION functinname ; Example: DROP FUNCTION getbalance ; Output: Functin drpped. Packages A package is ne kind f database bject. It is used t grup tgether lgically related bjects like variables, cnstants, cursrs, exceptins, prcedures and functins. A successfully cmpiled package is stred in racle database like prcedures and functins. Unlike prcedure and functins, package itself cannt be called. Example: In a banking system, all bjects assciated with transactin related activities can be gruped tgether in a package. Other package may cntain bjects assciated with sme ther 17

18 activities, like a prcedure debitacc and functin getbalance can be gruped tgether in sme cmmn package. Advantages Advantages f package are given belw: 1) Mdularity: Package prvides mdular apprach t prgramming. It is always t better t write mre than ne smaller prgrams instead f ne large prgram. 2) Security: Prgrams can be created t prvide varius functinalities and can be grup tgether int packages. Privileges can be granted t these packages rather than entire tables. S, privileges can be granted efficiently. 3) Imprved Perfrmance: An entire package, including all bjects within it, is laded int memry when the first cmpnent is accessed. This eliminates additinal calls t ther related bjects which results in reduced disk IO. S, perfrmance can be imprved. 4) Sharing f Cde: Once a package is created, bjects in that package can be shared amng multiple users. This reduces the redundant cding. 5) Overlading f prcedures and functins: Prcedures and functins can be verladed using packages. Structure f a Package A package cntains tw sectins: 1) Package Specificatin 2) Package Bdy While creating packages, package specificatin and package bdy are created separately. 1) Package Specificatin: Varius bjects (like variables, cnstants etc..) t be held by package are declared in this sectin. This declaratin is glbal t the package, means accessible frm anywhere in the package. CREATE OR REPLACE PACKAGE packagename IS -- Package Specificatin END packagename; Package specificatin cnsists f list f variables, cnstants, functins, prcedures and cursrs. Example 14 : Create a package transactin that cntains prcedure debitacc and functin getbalance created earlier. CREATE OR REPLACE PACKAGE transactin 18

19 Output: IS PROCEDURE NUMBER) ; FUNCTION NUMBER ; END transactin ; Package Created. debitacc ( n IN Accunt.Acc_N%TYPE, amunt IN getbalance (n IN Accunt.Acc_N%TYPE) RETURN 2) Package Bdy: It cntains the frmal definitin f all the bjects declared in the specificatin sectin. CREATE OR REPLACE PACKAGE BODY packagename IS -- package bdy END packagename; If a package cntains nly variables, cnstants and exceptins then package bdy is ptinal. Example 15 : Create a package bdy fr package transactin that cntains prcedure debitacc and functin getbalance created earlier. CREATE OR REPLACE PACKAGE BODY transactin IS -- define prcedure debitacc CREATE OR REPLACE PROCEDURE debitacc (n IN Accunt.Acc_N%TYPE, amunt IN NUMBER) IS bal Accunt.Balance%TYPE ; newbalance Accunt.Balance%TYPE ; SELECT Balance INTO bal FROM Accunt WHERE Acc_N = n ; newbalance := bal - amunt ; UPDATE Accunt SET balance = newbalance WHERE Acc_N = n ; dbms_utput.put_line( Accunt n debited.. ); END ; -- define functin getbalance CREATE OR REPLACE FUNCTION getbalance (n IN Accunt.Acc_N%TYPE ) RETURN NUMBER IS bal Accunt.Balance%TYPE ; SELECT Balance INTO bal FROM Accunt WHERE Acc_N = n ; 19

20 RETURN bal ; END ; END transactin ; Output: Package bdy created. Package bdy is created, bjects cntained in package are stred in Oracle database. Referencing a Package Subprgram T access bjects specified inside a package, fllwing syntax can be used. packagename.bject The use f. (dt) t cmbine package name and prcedure name t access prcedure. Example 16 : Prvide statement t debit an accunt A01 by amunt EXEC transactin.debitacc ( A01, 1000); Output: Accunt A01 debited.. Example 17 : Prvide statement t getbalance fr an accunt A01. SELECT transactin.getbalance ( A01 ) FROM dual ; Output: TRANSACTION.GETBALANCE ( A01 ) It is pssible t have same name fr tw different bjects held by tw different packages. In this situatin, package name prvides unique identificatin between such bjects. Destrying a Package DROP PACKAGE [ BODY ] packagename ; If BODY ptin is prvided, bdy f the specified package is deleted and leaves package specificatin unchanged. If BODY ptin is nt prvided, bth sectins f the package are deleted. Triggers A trigger is a grup r set f SQL and PLSQL statements that are executed by Oracle itself. The main characteristic f the trigger is that it is fired autmatically when DML statements like Insert, Delete, and Update is executed n a table. The advantages f triggers are as given belw: T prevent misuse f database. T implement autmatic backup f the database. T implement business rule cnstraints, such as balance shuld nt be negative. Based n change in ne table, we want t update ther table. T track the peratin being perfrmed n specific tables with details like peratin, time when it is perfrmed, user name wh perfrmed it, etc.. 20

21 Difference between Triggers and Prcedures: Triggers Prcedures Triggers are invked implicitly. Prcedures need t invke by users explicitly. Trigger cannt accept parameters. Prcedures can accept parameter. Trigger cannt return a value. Prcedures can return values Trigger can nly be executed, whenever an event (insert, delete, and update) is fired n the table n which the trigger is defined. T execute a prcedure, EXEC cmmand is used. Oracle allws t implement varius integrity cnstraints while creating a table t restrict data in tables. These cnstraints are called declarative integrity Cnstraints. Difference between Triggers and Declarative Integrity Cnstraints: Triggers Declarative Integrity Cnstraint Trigger is applicable t thse data that are laded befre the trigger is created. A cnstraint is applicable t all the data stred in a table. Trigger can implement transitinal Implementatin f transitinal cnstraint is cnstraint. nt pssible with declarative cnstraint. Example: ask fr passwrd fr specific peratin. Triggers d nt guarantee. Cnstraint guarantees all data in a table cnfrms the rules implemented. Structure f a Trigger A trigger cntains three basic sectins: 1) Triggering Event r Statement 2) Trigger Restrictin 3) Trigger Actin 1) Triggering Event r Statement: It is an SQL statement that causes a trigger t be fired. It can be INSERT, UPDATE r DELETE statement fr specific table. 2) Trigger Restrictin: It specifies a cnditin that must be true fr a trigger t fire. It is specified using WHEN clause. 3) Trigger Actin: It cntains SQL and PLSQL statements as well as stred prcedures that are executed when trigger is fired. This blck specifies actins that need t be perfrmed whenever a trigger is fired. Types f Triggers Triggers can be classified based n tw different criteria: 1) Based n number f times trigger actin is executed. a) Rw Trigger b) Statement Trigger 21

22 2) Based n timing when trigger actin is executed. a) Befre Trigger b) After Trigger 1) Based n number f times trigger actin is executed: Rw Trigger Fired each time the table is affected by the triggering statement. Example: If an UPDATE statement updates multiple rws f a table, a rw trigger is fired nce fr each rw affected by the UPDATE statement If n rws are affected by the triggering statement, a trigger will nt be executed. 2) Based n timing when trigger actin is executed: Befre Trigger Trigger is executed befre the triggering statement. Used t determines whether the triggering statement shuld be allwed t execute r nt. Statement Trigger Fired nly nce. Example: If an UPDATE statement updates multiple rws f a table, statement trigger is fired nly nce. Trigger will be executed nce, if n rws are affected by the triggering statement. After Trigger These types are used in cmbinatin, prvides ttal fur types f triggers: 1) Befre Statement: Execute trigger nce befre triggering statement. 2) Befre Rw: Execute trigger multiple times befre triggering statement. 3) After Statement: Execute trigger nce after triggering statement. 4) After Rw: Execute trigger multiple times after triggering statement. Creating a Trigger CREATE [OR REPLACE] TRIGGER [BEFORE AFTER] ON Trigger is executed after the triggering statement. Used when there is a need fr a triggering statement t cmplete executin befre trigger. trigger_name [INSERT UPDATE DELETE [f clumnname] ] table_name [REFERENCING [OLD AS ld, NEW AS new] ] [FOR EACH ROW [WHEN cnditin] ] DECLARE Declaratin sectin Executable statements EXCEPTION Exceptin handling END ; 22

23 Explanatin f Keywrds: Keywrd REPLACE BEFORE OF clumnname AFTER DELETE INSERT UPDATE ON REFERENCING FOR EACH ROW WHEN cnditin Specifies.. Re- creates the trigger if it already exists. Befre updating the table, trigger shuld be fired. This clause is used when yu want t trigger an event nly when a specific clumn is updated. This clause is mstly used with update triggers. After updating the table, trigger shuld be fired. Indicates that trigger will be fired n DELETE peratin. Indicates that trigger will be fired n INSERT peratin. Indicates that trigger will be fired n UPDATE peratin. Specifies table r view fr which trigger is defined. Specifies crrelatin names OLD and NEW- that specify ld and new value fr a recrd during triggering statement. Fr UPDATE, bth are applicable; fr INSERT nly NEW is applicable; fr DELETE nly OLD is applicable. Creates ROW type trigger. If mitted, statement type trigger is created. Specifies cnditin as a trigger restrictin. The trigger is fired nly fr rws that satisfy the cnditin specified. This clause is valid nly fr rw type triggers. Example 18 : Using trigger, display message if balance is negative during insert peratin n Accunt table. CREATE OR REPLACE TRIGGER balnegative BEFORE INSERT ON Accunt FOR EACH ROW Output: END ; IF :NEW.Balance < 0 THEN dbms_utput.put_line ( Balance is negative.. ); END IF ; Trigger created. Example 19 : Insert a new recrd in Accunt table having balance INSERT INTO Accunt values ( A07, -1000, Vrl ) ; Output: Balance is negative.. The message Balance is negative.. indicates that trigger has executed befre the insert peratin. Destrying a Trigger DROP TRIGGER triggername ; 23

24 Example: DROP TRIGGER balnegative ; Output: Triggered drpped. RAISE_APPLICATION_ERROR prcedure Trigger cannt use cmmands like ROLLBACK, COMMIT and SAVEPOINT. S, it is nt pssible t und sme peratin. Oracle prvides a prcedure called RAISE_APPPLICATION_ERROR that can be used t generate errrs and display user-defined errr messages. When such kind f errr is generated, prgram will simply terminate. S, this prcedure can be used with trigger t prevent executin f peratin which break integrity rules. RAISE_APPLICATION_ERROR ( errrnumber, errrmessage) ; errrnumber is negative number indicating errr. errrmessage is a character string. This prcedure raises an errr, terminates sub-prgram, rllback any database changes made by that sub-prgram and display user defined errrnumber and errrmessage. Example 20 : Using trigger, prevent the insertin peratin if balance being inserted is negative. CREATE OR REPLACE TRIGGER balnegative BEFORE INSERT ON Accunt FOR EACH ROW IF :NEW.Balance < 0 THEN RAISE_APPLICATION_ERROR ( , Balance is negative ) ; END IF ; END ; Output: Trigger created. Example 21 : Insert a new recrd in Accunt table having balance INSERT INTO Accunt VALUES ( A08, -5000, Vrl ); Output: INSERT INTO Accunt VALUES ( A08, -5000, Vrl ); ERROR at line 1: ORA-20000: Balance is negative Disadvantage f trigger: It is nt pssible t track r debug triggers. Triggers can execute every time sme field in database is updated. If a field is likely t be updated ften, it is a system verhead. It is easy t view table relatinships, cnstraints, indexes, stred prcedure in database but triggers are difficult t view. 24

25 T prcess table data, it must be stred int variables and this task perfrmed by SELECT INTO statement. But, this statement suffers frm a limitatin that it can stre data nly frm a single recrd by using WHERE clause. It cannt be used with multiple recrds. S, if there is a need t simply display all recrds f an Accunt table using PLSQL blck, it is nt pssible. Cursr prvides slutin t this prblem. Cursrs Whenever an SQL statement is executed, Oracle reserves a private SQL area in memry. The data required t execute the statement are laded in this memry area frm the hard disk. Once data are stred in memry, they are prcessed as per the peratin. After prcessing is finished, updated data are stred back t the hard disk and memry is freed. Cursr cmes int picture fr this kind f prcessing. A Cursr is an area in memry where the data required t execute SQL statement. S, a cursr referred as wrk area. S, the size f the cursr will be the same as a size t hld this data. Active Data Set: The data (Set f rws) that is stred in the cursr is called Active Data Set. Result Set: Data is stred in cursr because f sme SQL statement. S, it is called Result Set. Current Rw: The rw that is being prcessed is called the Current Rw. Rw Pinter: A pinter that is used t track the current rw is knwn as Rw Pinter. Cursr Attributes: Multiple cursr variables are used t indicate the current status f the prcessing being dne by the cursr. These kinds f variables are knwn as Cursr Attributes. Varius cursr attributes are described in given belw table: Attribute Name Descriptin %ISOPEN %ISFOUND %NOTFOUND %ROWCOUNT If cursr is pen, returns TRUE. Else returns False. If recrd fetched successfully, returns TRUE. Else returns FALSE. If recrd was nt fetched successfully, returns TRUE. Else returns FALSE. Returns number f recrds prcessed by the cursr. There are tw types f cursrs in PLSQL: 1) Implicit Cursr 2) Explicit Cursr Accunt: Acc_N Balance B_Name A RJT A AHMD A SRT A RJT 25

26 1) Implicit Cursr: A cursr is called an Implicit Cursr, if it is pened by Oracle itself t execute SQL Statement like SELECT, INSERT, UPDATE r DELETE. It is pened and managed by Oracle itself. S, user needs nt t care abut it. We cannt use implicit cursrs fr user defined wrk. Oracle perfrms fllwing peratin t manage an implicit cursr: Reserve an area in memry t stre data required t execute SQL statement. Occupy this area with required data. Prcesses data. Frees memry area by clses a cursr, when prcessing is cmpleted. The syntax t use attributes f implicit cursr can be given as: SQL%AttributeName The value f the cursr attribute always refers t the SQL cmmand that was executed mst recently. Befre pen implicit cursr, its attribute cntains NULL as value. The meaning f cursr attribute in cntext f implicit cursr are described in given belw table: Attribute SQL%ISOPEN SQL%FOUND SQL%NOTFOUND SQL%ROWCOUNT Descriptin Always returns FALSE, because Oracle autmatically clses cursrs after executing SQL statement. If SELECT fund any recrd r INSERT, UPDATE and DELETE affected any recrd then return TRUE. Else returns FALSE. If SELECT fund n any recrd r INSERT, UPDATE and DELETE affected n any recrd then returns TRUE. Else returns FALSE. Returns number f recrds prcessed by SELECT, UPDATE, INSERT r DELETE peratins. Example 22 : In Accunt table, branch names are stred in upper case letters. Cnvert branch name int lwer case letters fr a branch specified by the user. Als display hw many accunts are affected. DECLARE -- Declare required variables branch Accunt.B_Name%TYPE; -- read a number frm the user branch := &branch; -- mdify branch name UPDATE Accunt SET B_Name = LOWER(branch) WHERE B_Name = branch; -- display number f recrd updated if any IF SQL%FOUND THEN dbms_utput.put_line( Ttal SQL%ROWCOUNT recrds are updated. ); 26

27 ELSE dbms_utput.put_line( Given branch nt available. ); END IF ; END; Output 1: Enter value fr branch: surat Given branch nt available. Output 2 : Enter value fr branch: RJT Ttal 2 recrds are updated. If yur Accunt table defines as freign key referencing Branch table then this kind f update peratin will get failed. 2) Explicit Cursr: A cursr is called Explicit Cursr, if it is pened by user t prcess data thrugh PLSQL blck. It is pened by user. S, user has t take care abut managing it. It is used when there is a need t prcess mre than ne recrd individually. Even thugh the cursr stres multiple recrds, nly ne recrd can be prcessed at a time, which is called as current rw. Fllwing steps required t manage an explicit cursr: Declare a cursr Open a cursr Fetching data Prcessing data Clsing cursr 1) Declare a Cursr: CURSOR cursrname IS SELECT. ; A cursr with cursrname is declared. It is mapped t a query given by SELECT statement. Here, nly cursr will be declared. N any memry is allcated yet. Example: CURSOR cursracc IS SELECT Acc_N, Balance, B_Name FROM Accunt ; 2) Open a Cursr: Once cursr is declared we can pen it. When cursr is pened fllwing peratins are perfrmed: Memry is allcated t stre the data. Execute SELECT statement assciated with cursr. Create active data set by retrieving data frm table. Set the cursr rw pinter t pint t first recrd in active data set. 27

28 OPEN cursrname ; 3) Fetching Data: We cannt prcess selected rw directly. We have t fetch clumn values f a rw int memry variables. This is dne by FETCH statement. FETCH cursrname INTO variable1, variable2. ; Retrieve data frm the current rw in the active data set and stres them in given variables. Data frm a single rw are fetched at a time. After fetching data, updates rw pinter t pint the next rw in an active data set. Variables shuld be cmpatible with the clumns specified in the SELECT statement. Example: FETCH cursracc INTO n, balance, bname ; Fetched accunt number, balance and branch name frm current rw in active data set and stre them in respective variables. T prcess mre than ne recrd, the FETCH statement is enclsed within lp like LOOP END LOOP can be used. 4) Prcessing data: This step invlves actual prcessing f current rw by using PLSQL as well as SQL statements.. 5) Clsing Cursr: A cursr shuld be clsed after the prcessing f data cmpletes. Once yu clse the cursr it will release memry allcated fr that cursr. If user frgets t clse the cursr, it will be autmatically clsed after terminatin f the prgram. CLOSE cursrname ; The syntax t use attributes f explicit cursr can be given as: SQL%AttributeName The meaning f cursr attribute in cntext f explicit cursr are described in given belw table: Attribute Descriptin SQL%ISOPEN SQL%FOUND SQL%NOTFOUND SQL%ROWCOUNT If explicit cursr is pen, returns TRUE. Else Return False. If recrd was fetched successfully in last FETCH statement then return TRUE. Else returns FALSE indicating n mre recrds available in active data set. If recrd was nt fetched successfully in last FETCH statement returns TRUE. Else returns FALSE. Returns number f recrds fetched frm active data set. It is set t ZERO when cursr is pened. 28

29 Example 23 : Transfer all the accunts belnging t RJT branch frm Accunt table int anther table Accunt_RJT having nly 2 clumn Acc_N and Balance. If table is nt available then first create it. DECLARE -- declare a cursr CURSOR cursracc IS SELECT Acc_N, Balance, B_Name FROM Accunt ; --declare required variables n Accunt.Acc_N%TYPE ; balance Accunt.Balance%TYPE ; branch Accunt.B_Name%TYPE ; --pen a cursr OPEN cursracc ; --if cursr is pened successfully then prcess data --Else display errr message IF cursracc%isopen THEN --traverse lp LOOP --fetch data frm cursr rw int variavbles FETCH cursracc INTO n, balance, branch; --if n recrd available in active data set then exit frm lp EXIT WHEN cursracc%notfound ; --prcess data. If recrd belngs t RJT branch, transfer it IF branch = RJT THEN -- insert recrd int Accunt_RJT table INSERT INTO Accunt_RJT VALUES(n, balance); --delete recrd frm the Accunt table DELETE FROM Accunt WHERE Acc_N = n ; END IF ; END LOOP; --cmmit peratins COMMIT; ELSE dbms_utput.put_line ( Cursr cannt be pened. ) ; END IF ; END ; After executing this PLSQL blck, display data frm Accunt and Accunt_RJT tables. Example 24 : Display data frm the Accunt table. SELECT * FROM Accunt ; Output: Acc_N Balance B_Name A AHMD A SRT 29

30 Example 25 : Display data frm the Accunt_RJT table. SELECT * FROM Accunt_RJT; Output: Acc_N Balance A A Cursr FOR Lp FETCH statement can fetch data frm single rw f an active data set. But, there will be a need t prcess multiple rws mst f the times. S, FETCH statement is enclsed within a lp t prcess multiple rws. Fr that racle prvide anther lp statement that is a variatin f the basic FOR lp. FOR variable IN cursrname LOOP -- Execute cmmands END LOOP; Abve syntax perfrms fllwing peratins autmatically: A given variable is created f the %ROWTYPE and refer t the entire rw. Specified cursr is pened. Data frm the rw f the active data set are fetched int given variable fr each iteratin f the lp. Exits frm the lp and clses the cursr. Here, variable f %ROWTYPE is refer t entire rw. The individual fields f the recrd can be accessed as given belw: variablename.clumnname Example 26 : Transfer all the accunts belnging t RJT branch frm Accunt table int anther table Accunt_RJT having nly 2 clumn Acc_N and Balance. If table is nt available then first create it. DECLARE -- declare a cursr CURSOR cursracc IS SELECT Acc_N, Balance, B_Name FROM Accunt ; --use f a cursr FOR lp. varacc is declared as a type f %ROWTYPE FOR varacc IN cursracc LOOP --prcess data. If recrd belngs t RJT branch, transfer it IF varacc.b_name = RJT THEN -- insert recrd int Accunt_RJT table INSERT INTO Accunt_RJT VALUES(varAcc.ACC_N, varacc.balance); 30

31 --delete recrd frm the Accunt table DELETE FROM Accunt WHERE Acc_N = varacc.acc_n ; END IF ; END LOOP; --cmmit peratins COMMIT; ELSE dbms_utput.put_line ( Cursr cannt be pened. ) ; END IF ; END ; Same utput can be bserve as given example 3 and 4 after executing this PLSQL blck. Parameterized Cursrs Up t this pint, active data set cntains all the recrds frm the given table. Nw if we want t create an active data set that cntains nly selected recrds frm the given table. Fr example, we want t create an active data set that cntains recrds belnging t RJT branch nly nt all recrds f Accunt table. Fr this purpse, racle allws t pass parameters t cursr that can be used t prvide cnditin with WHERE clause. If parameters are passed t cursr, that cursr is called parameterized cursr. Syntax t declare parameterized cursr is: CURSOR cursrname (variablename datatype) IS SELECT.. ; While pening cursr, parameter can be passed using fllwing syntax: OPEN cursrname (value variable expressin); Example 27 : Transfer accunts f RJT branch f Accunt t Accunt_RJT table. DECLARE -- declare a cursr CURSOR cursracc (brname Accunt.B_Name%TYPE) IS SELECT Acc_N, Balance, B_Name FROM Accunt WHERE B_Name = brname; --declare required variables n Accunt.Acc_N%TYPE ; balance Accunt.Balance%TYPE ; branch Accunt.B_Name%TYPE ; --pen a cursr OPEN cursracc ( RJT ); --if cursr is pened successfully then prcess data --Else display errr message IF cursracc%isopen THEN --traverse lp 31

32 LOOP --fetch data frm cursr rw int variavbles FETCH cursracc INTO n, balance, branch; --if n recrd available in active data set then exit frm lp EXIT WHEN cursracc%notfound ; --prcess data --n need t check whether recrd belngs t RJT branch -- insert recrd int Accunt_RJT table INSERT INTO Accunt_RJT VALUES(n, balance); --delete recrd frm the Accunt table DELETE FROM Accunt WHERE Acc_N = n ; END LOOP; --cmmit peratins COMMIT; ELSE dbms_utput.put_line ( Cursr cannt be pened. ) ; END IF ; END ; Observe the data f Accunt and Accunt_RJT tables. Exceptin Handling Run-time errrs can be handled in sme useful way rather than getting system specific message and terminating prgram directly. It s called exceptin handling. Built-In Exceptin Handler An errr ccurs at run-time is called an exceptin. These errrs may invlve the peratin like divide by zer, access t unauthrized data, etc.. in PLSQL blck. A blck f cde that attempts t reslve exceptins is knwn as exceptin handler. Fllwing diagram shws the wrking f exceptin handler: Exceptin Scan PLSQL blck Yes Exceptin Handling Sectin Available? N Cde Available t Handle Exceptin? N Default Exceptin Handling Yes User-defined Exceptin Handling Stp 32

33 There are tw types f exceptin: 1) System Exceptin: In PLSQL, varius run-time errrs are assciated with different exceptins. These types f exceptins are knwn as system exceptin. 2) User-defined Exceptin: User als can define their wn exceptin is knwn as user-defined exceptin. Exceptin handler scans the PLSQL blck t check existence f the Exceptin Handling sectin within blck. If it is available then it is checked t find the cde t handle exceptin. EXCEPTION WHEN exceptinname THEN -- cde t handle exceptin. Here, it cntains mre than n WHEN clauses. An exceptinname is a character string represents an exceptin t be handled. If exceptin handling sectin is available and an exceptin is raised then the apprpriate cde is executed. Otherwise an exceptin is handled using default exceptin handling cde that is simply displaying an errr message r terminating the prgram. Types f Exceptins Exceptin can be either System Exceptin (Pre-defined Exceptin ) r User-define Exceptin. System Exceptins can be further divide in t tw parts: 1) Named Exceptins 2) Numbered Exceptins 1) Named Exceptins: Particular name given t sme cmmn system exceptins is knwn as Named Exceptin. Oracle has defined 15 t 20 named exceptins. Sme f the named exceptins are listed in belw table: Exceptin INVALID_NUMBER NO_DATA_FOUND ZERO_DIVIDE TOO_MANY_ROWS LOGIN_DENIED NOT_LOGGED_ON INVALID_CURSOR PROGRAM_ERROR DUP_VAL_ON_INDEX VALUE_ERROR OTHERS Raised When TO_NUMBER functin failed in cnverting string t number. SELECT INTO statement culdn t find data. Divide by zer errr ccurred. SELECT INTO statement fund mre than ne recrd. Invalid usename r passwrd fund while lgging. Statements tried t execute withut lgging. A cursr is attempted t use which is nt pen. PLSQL fund internal prblem. Duplicate value fund in clumn defined as unique r primary key. Errr ccurred during cnversin f data. Stands fr all ther exceptins. 2) Numbered Exceptins: These exceptins are identified by using negative signed number, such as Oracle has defined mre than numbered exceptins. 33