Database links: Views:

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1 Database links: Views: Allows to connect to remote databases Can be public or private Public can be used by anyone and private is available only for owner of the object. Can point to host in the tns entry or can have descrip;on in the host clause Public database links without fully qualified username and password cannot be used in dbms jobs DBA_DB_LINKS gives informa;on about database links Syntax: Create [public] database link <dblink-name> connect to [<username>] [iden;fied by <passwd>] using <'hostdescrip;on'>; View is a logical representa;on of data. It is a query which runs against the base tables to get the data. If we use group func;ons in the select clause we need to define column alias Select statement cannot have order by We can change the data in underlying tables through views. If the column is defined using single row func;on we cannot update the column If u want to restrict the update the data on which the user have the access we can use with check op;on. To create a read-only view use with read only op;on Complex views will not enable you to change the data in any of the base tables if all the constraints are not defined properly. To modify the view use create or replace To compile the view user alter view <viewname> compile; To check for the errors use DBA_ERRORS view. DBA_VIEWS gives informa;on about views. Syntax: create view <viewname> (select query) [with check op;on constraint <constraint-name>][with readonly];

2 Materialized views: A materialized view is a replica of target table at a point of ;me. Used for repor;ng applica;ons or OLAP env Materialized view can be readonly,updatable materialize view and writeable materialized views Updatable materialized view must belong to a materialized group Writable materialized view is create with for update clause but it is not part of materialized group Materialized views can be refreshed fully or in incremental To setup an incremental refresh on mv's we need to have a primary key, mv log and logging enabled on target table. Dbms_mview.refresh package used to refresh the views Prebuilt op;on can be used for the larger tables to avoid pulling informa;on for remote database over the network. Materialized views can be par;;oned,indexes can be created on materialized views If materialized view uses a simple select statement or if a master table has lob then we need to go for full refresh If materialized view is a complex view and it has large data then we need to go for incremental or fast refresh execute DBMS_MVIEW.REFRESH('<view-name',cf,atomic_refresh=>false); Syntax: Synonym: Create materialized view <view-name> [for update] [query rewrite] [parnnon by <rangelist> (parnnon p1 values less than(<value)..] As (<select statement>) [with prebuilt]; To create materialize view log Create materialized view log on <table-name>; Synonym can be a public or private Create synonym <synonym-name> for <owner.object-name>; Create public synonym <synonym-name> for <owner.object-name>; Used as short cut.

3 Sequence: A sequence is a database object which generates integers according to rules specified at the ;me of crea;ng sequence Syntax: Create sequence <sequence-name> start with <ini;tal-value> increment by <value> [maxvalue <value> cyclenocycle]; Sequencename.currval to give the current value, sequencename.nextval to generate next value Sequence gaps occurs when you issue rollback and during system crash. Trigger: A trigger is a PLSQL block which fires when event occurs. Event can be dml statements are performed on tables or the user logins to database or database startup or shutdown. CREATE [OR REPLACE ] TRIGGER trigger_name {BEFORE AFTER INSTEAD OF } {INSERT [OR] UPDATE [OR] DELETE} [OF col_name] ON table_name [REFERENCING OLD AS o NEW AS n] [FOR EACH ROW] WHEN (condi;on) --- sql statements

4 PLSQL: PLSQL is a combina;on of SQL along with the procedural features of programming languages. PLSQL is a block structured language, meaning that PLSQL programs are divided and wrieen in logical blocks of code. PLSQL block consists of three parts. 1. Declara;ons: This sec;on starts with keyword declare. It is an op;onal sec;on and defines all variables, cursors, subprograms and other elements to be used in the program. 2. Executable commands: This sec;on is enclosed between begin and end and it is a mandatory sec;on. It consists of executable PLSQL statements of the program. It should have atleast one executable line of code which may be just a null command to indicate that nothing should be executed. 3. Excep;onal Handling: This sec;on start with the keyword EXCEPTION and its op;onal. Contains excep;ons that handles errors in the program. Every PLSQL statement ends with a semicolon (;). PLSQL blocks can be nested within other PLSQL blocks using and END. Here is the basic structure of a PLSQL block: DECLARE <declara;ons sec;on> <executable command(s)> EXCEPTION <excep;on handling>

5 Variable A variabe is nothing but a name given to a storage area that out programs can manipulate. Each variable in PLSQL has a specific datatype which determines the size and layout of the variables memory. Variable declara;on in PLSQL <variable_name> [constant] <datatype> [NOT NULL] [:= DEFAULT ini;al_value] Oracle defined DATATYPES: NUMBER,INTEGER,CHAR,VARCHAR2,LONG,ROWID,BOOLEAN,DATE,BLOB,CLOB,BFILE User defined DATATYPES: SUBTYPE name is CHAR(20) SUBTYPE INTEGER is NUMBER(38,0) Example of Variable Declara;ons: Sales number(10,2) Name varchar2(25) Address varchar2(100) Saluta;on name; A constat is declared using constant keyword. It requires an ini;al value and doesn't allow the value to be changed. Declaring a constant PI CONSTANT NUMBER := ;

6 ARRAY: PLSQL provides a data structure called VARRAY, which can store a fixed-size sequen;al collec;on of elements of same datatype. VARRAY consists of con;guous memory loca;ons. The lowest address corresponds to the first element and the highest address to the last element. Below is the syntax to create Varray type. Create or replace type <varray_type_name> is varray(n) of <element_type> Record: A PLSQL data structure that can hold data items of different kinds. Records consists of different fields, similar to a row of a database table. The %ROWTYPE aeribute enables a programmer to create a table based record. <variable-name> <table-name>%rowtype. Cursor: Oracle creates a memory area known as context area, for processing an SQL statement. A cursor is a pointer to this contenxt area.a cursor holds the rows returned b a SQL statement. There are two types of cursors. 1. IMPLICIT CURSORS: IMPLICIT CURSORS are automa;cally created by oracle whenever a SQL statement is executed, when there is no explicit curor for the statement. Whenever a DML statement (INSERT,DELETE and UPDATE) is issues, an implicit cursor is associated with this statement. For insert opera;on the cursor hold the data to be inserted. For update opera;ons the cursor iden;fied the rows that would be affected. 2. Explicit cursors: Explicit cursors are programmer defined cursors for gaining more control over the context area. Syntax for crea;ng explicit curor: CURSOR <cursor_name> is <select statement> CURSOR has aeributes %FOUND,%NOTFOUND which returns true if any records is affected bynot affected by DML statement %ISOPEN checks whether the cursor is opened or closed and %ORWCOUNT returns the number of records affected by DML statement.

7 CondiNons: IF STATEMENT: IF CONDITION THEN <ac;ons>; IF-THEN-: IF condi;on THEN <ac;ons>; <ACTIONS>; END IF: IF-THEN-ELSIF: IF CONDITION THEN <ac;ons>; ELSIF condi;on THEN <ac;ons>; <ac;ons>; CASE: CASE selector WHEN 'value1' THEN ac;ons; WHEN 'value2' THEN ac;ons; WHEN 'value3' THEN ac;ons;.. <ac;ons; END CASE; If (a<=20) then c:=c+1; IF color = red THEN dbms_output.put_line('you have choosen a red car'); dbms_output.put_line('please choose color of your car'); IF ( a = 10 ) THEN dbms_output.put_line('value of a is 10' ); ELSIF ( a = 20 ) THEN dbms_output.put_line('value of a is 20' ); ELSIF ( a = 30 ) THEN dbms_output.put_line('value of a is 30' ); dbms_output.put_line('none of the values is matching'); DECLARE grade char(1) := 'A'; CASE grade when 'A' then dbms_output.put_line('excellent'); when 'B' then dbms_output.put_line('very good'); when 'C' then dbms_output.put_line('well done'); when 'D' then dbms_output.put_line('you passed'); when 'F' then dbms_output.put_line('beeer try again'); else dbms_output.put_line('no such grade'); END CASE;

8 Procedure: Procedure is named PLSQL block which can have sequence of tasks to perform. CREATE [OR REPLACE] PROCEDURE proc_name [list of parameters] IS Declara;on sec;on Execu;on sec;on EXCEPTION Excep;on sec;on FuncNon: A func;on is a named plsql block which is similar to a procedure but returns value. CREATE [OR REPLACE] FUNCTION func;on_name [parameters] RETURN return_datatype; IS Declara;on_sec;on Execu;on_sec;on Return return_variable; EXCEPTION excep;on sec;on Return return_variable;

9 Basic Loop: Basic loop structure encloses sequence of statements in between loop and end loop statements.with each itera;on the sequence of statements is executed and then contro resumes at the top of the loop.exit statement or exit when statement is required to break the loop. A while loop repeatedly executes statements as long as condi;on is true.it test the condi;on before execu;ng the loop. A for loop allows to repeatedly executes the statements every ;me the condi;on is sa;sfied. DECLARE x number := 10; LOOP dbms_output.put_line(x); x := x + 10; IF x > 50 THEN exit; END LOOP; -- auer exit, control resumes here dbms_output.put_line('auer Exit x is: ' x); DECLARE a number(2) := 10; WHILE a < 20 LOOP dbms_output.put_line('value of a: ' a); a := a + 1; END LOOP; DECLARE a number(2); FOR a in LOOP dbms_output.put_line('value of a: ' a); END LOOP;

10 declare sal_v emp.sal%type; emp_no emp.empno%type; begin select sal,empno into sal_v,emp_no from emp where empno=10; dbms_output.put_line('salary of employee id ' emp_no ' is ' sal_v); end; create procedure simple_proc is --declare sal_v emp.sal%type; emp_no emp.empno%type; begin select sal,empno into sal_v,emp_no from emp where empno=10; dbms_output.put_line('salary of employee id ' emp_no ' is ' sal_v); end; create or replace procedure simple_proc is --declare sal_v emp.sal%type; emp_no emp.empno%type; sal_total number(10); begin select sal,empno into sal_v,emp_no from emp where empno=10; if(emp_no=10) then sal_total:=sal_v+1000; else sal_total:=sal_v+2000; end if; dbms_output.put_line('salary of employee id ' emp_no ' is ' sal_total); end;

11 CREATE OR REPLACE TRIGGER emp_audit BEFORE INSERT OR DELETE OR UPDATE ON emp FOR EACH ROW ENABLE DECLARE v_user varchar2(30); v_date varchar2(30); SELECT user,to_char(sysdate,'dd-mon-yy HH24:MI:SS') INTO v_user,v_date FROM DUAL; IF INSERTING THEN INSERT INTO emp_audit(new_name,old_name,user_name,entry_date,opera;on ) values(:new.ename,null,v_user,v_date,'insert'); ELSIF DELETING THEN INSERT INTO emp_audit(new_name,old_name,user_name,entry_date,opera;on ) values(null, :OLD.ename,v_user,v_date,'update'); ELSIF UPDATING THEN INSERT INTO emp_audit(new_name,old_name,user_name,entry_date,opera;on ) values(:new.ename, :OLD.ENAME,v_user,v_date,'delete'); CREATE OR REPLACE FUNCTION check_sal(emp_id emp.empno %TYPE) RETURN varchar2 IS dept_id emp.deptno%type; salary emp.sal%type; avg_sal emp.sal%type; output varchar2(50); SELECT sal INTO salary FROM emp WHERE empno=emp_id; SELECT avg(sal) INTO avg_sal FROM emp; IF salary > avg_sal THEN return 'salary of employee is greater than average salary'; RETURN 'salary of employee is less than average salary';

12 CREATE or REPLACE PROCEDURE proc_bonus IS --DECLARE bonus number(5,2); sal emp.sal%type; CURSOR c_emp_dept IS SELECT e.ename,e.sal,d.deptno,d.loc FROM emp e join dept d ON e.deptno=d.deptno; v_emp_dept c_emp_dept%rowtype; OPEN c_emp_dept; LOOP FETCH c_emp_dept into v_emp_dept; IF(v_emp_dept.deptno=10) THEN CASE v_emp_dept.loc WHEN 'NEW YORK' THEN sal:=v_emp_dept.sal+1000; WHEN 'DALLAS' THEN sal:=v_emp_dept.sal+500; WHEN 'CHICAGO' THEN sal:=v_emp_dept.sal+800; sal:=v_emp_dept.sal; END CASE; DBMS_OUTPUT.PUT_LINE('Employee ' v_emp_dept.ename ' total salary is ' sal); sal:=v_emp_dept.sal+600; EXIT WHEN c_emp_dept%nowound; END LOOP; Create or replace type emp_ids is varray(10) of number(5); create or replace procedure total_emp(emp_id in emp_ids) is --declare sal_v emp.sal%type; sal_total number(5); emp_no emp.empno%type; cursor emp_cur is select sal,empno from emp where empno in(select column_value from table(emp_id)); emp_v emp_cur%rowtype; begin open emp_cur; loop --select sal,empno into sal_v,emp_no from emp_cur ; fetch emp_cur into emp_v; if(emp_v.empno=10) then sal_total:=emp_v.sal+1000; else sal_total:=emp_v.sal+2000; end if; exit when emp_cur%nowound; --update emp set sal=sal_total where empno=60; dbms_output.put_line('total salary of employee id ' emp_v.empno ' is ' sal_total); dbms_output.put_line(sal_total); end loop; end; Create type emp_ids is varray(10) of number(5);

13 CREATE OR REPLACE FUNCTION check_sal(emp_id emp.empno%type) RETURN number IS dept_id emp.deptno%type; salary emp.sal%type; avg_sal emp.sal%type; emp_no emp.empno%type; output varchar2(50); SELECT sal,empno INTO salary,emp_no FROM emp WHERE empno=emp_id; SELECT avg(sal) INTO avg_sal FROM emp; IF salary > avg_sal THEN return 1; --return 'salary of employee ' emp_no ' is greater than average salary'; RETURN 0; create or replace procedure total_emp(emp_id in emp_ids) is --declare sal_v emp.sal%type; sal_total number(5); emp_no emp.empno%type; cursor emp_cur is select sal,empno from emp where empno in(select column_value from table(emp_id)); emp_v emp_cur%rowtype; begin open emp_cur; loop --select sal,empno into sal_v,emp_no from emp_cur ; fetch emp_cur into emp_v; if(check_sal(emp_v.empno)=0) then if(emp_v.empno=10) then sal_total:=emp_v.sal+1000; else sal_total:=emp_v.sal+2000; end if; else sal_total:=emp_v.sal; end if; exit when emp_cur%nowound; --update emp set sal=sal_total where empno=60; dbms_output.put_line('total salary of employee id ' emp_v.empno ' is ' sal_total); dbms_output.put_line(sal_total); end loop; end;

14 Package: A package is a database object that groups logically related named PLSQL blocks. A package will have two mandatory parts: 1. Package specifica;on: Specifica;on is the interface to the package. It just declares the type,variables,constants,cursors and subprograms that can be referenced outside the package. 2. Package body: Package body has the codes for various methods declared in the package speciica;on and other private variables Notes: Dba_errors is used to retrieve informa;on about the errors associated with the object. Dba_Dependencies gives informa;on about dependent objects. Alter <procedurefunc;ontriggerpackageview> compile to recompile the the invalid object. Drop <object-type> <object-name> to drop the objects. Execute <procedure-name>[(<input-argument>)] to execute a stored procedure. Set serveroutput on should be executed to display the output message from dbms_output.put_line. create <object-type> privilege should be granted to a user to create a specific object type. Select <func;on-name>[(<input-argument>)] from dual to execute a procedure. Execute <package_name>.<procedurefunc;on>[(<input-arguments>)] used to execute a subprogram of a package.

15 create or replace package demo_pkg AS procedure total_emp(emp_id in emp_ids); func;on check_sal(emp_id emp.empno%type) return number; end demo_pkg; create or replace package body demo_pkg as procedure total_emp(emp_id in emp_ids) is --declare sal_v emp.sal%type; sal_total number(5); emp_no emp.empno%type; cursor emp_cur is select sal,empno from emp where empno in (select column_value from table(emp_id)); emp_v emp_cur%rowtype; begin open emp_cur; loop --select sal,empno into sal_v,emp_no from emp_cur ; fetch emp_cur into emp_v; if(check_sal(emp_v.empno)=0) then if(emp_v.empno=10) then sal_total:=emp_v.sal+1000; else sal_total:=emp_v.sal+2000; end if; else sal_total:=emp_v.sal; end if; exit when emp_cur%nowound; --update emp set sal=sal_total where empno=60; dbms_output.put_line('total salary of employee id ' emp_v.empno ' is ' sal_total); dbms_output.put_line(sal_total); end loop; end total_emp; FUNCTION check_sal(emp_id emp.empno%type) RETURN number IS dept_id emp.deptno%type; salary emp.sal%type; avg_sal emp.sal%type; emp_no emp.empno%type; output varchar2(50); SELECT sal,empno INTO salary,emp_no FROM emp WHERE empno=emp_id; SELECT avg(sal) INTO avg_sal FROM emp; IF salary > avg_sal THEN return 1; RETURN 0; END check_sal; end demo_pkg;

PL/SQL is a combination of SQL along with the procedural features of programming languages.

PL/SQL is a combination of SQL along with the procedural features of programming languages. (24 Marks) 5.1 What is PLSQL? PLSQL stands for Procedural Language extension of SQL. PLSQL is a combination of SQL along with the procedural features of programming languages. It was developed by Oracle