Oracle SQL. January 9, DaiMuHong

Transcription

1 Oracle SQL January 9, 2007 DaiMuHong 1

2 2. Basic Concepts and Commands Basic Concepts: Oracle Data Types 1. Number Number Any number Number(4) Integer, Max length 4, to 9999 Number(5,2) Decimal, such as Character Char(2) Length Fixed, such as PA, DC varchar2(30) Length Variable, such as Address 3. Date Date Regular Date, Minimum is 1 second Timestamp For time precision < 1 second 4. Long For any data with size > 4000 byte Such as photo, video clip 2

3 2. Basic Concepts and Commands Oracle database, SQL and SQL Plus SQL: Structured Query Language A 4 th Generation Language Used to access Database PL/SQL: SQL + Logic Control SQL Plus: An Oracle Database interface to execute SQL commands and PL/SQL programs 3

4 2. Basic Concepts and Commands Log on to SQL Plus Go to your Oracle Home directory, then bin/sqlplus.exe Logon to SQL Plus: User name: system, scott Password: tiger (default) To change password: Log on to SQL Plus, type command: SQL> password To Unlock Account: SQL> Alter user scott account unlock; For our example, password: tiger Leave Host String Empty To give SCOTT more power: Log on as SYSTEM SQL> grant DBA to scott; 4

5 2. Basic Concepts and Commands Running SQL commands in SQL Plus commands, Buffer, and Command file SQL> Select empno, ename, sal From Emp; 1. Not case sensitive 2. End with ; or / must be at the beginning of a new line 3. Can be written in more than 1 line 4. File can be saved to a file, called sql plus script 5. A file can contain multiple SQL SQL Plus command 5

6 2. Basic Concepts and Commands Basic SQL Command: Create table Drop table Alter table Select Insert Update Delete Commit: Save the modification made by Delete, insert or update Rollback: discard the modification 6

7 2. Basic Concepts and Commands Basic SQL Plus Commands: DESC, or DESCRIBE -- Used to find the table structure set pagesize 100 set linesize 80 set heading on/off -- Used to setup SQL Plus interface environment ed, or edit -- Used to edit a file spool /off -- Used to record all the text which shown in SQL Plus screen 7

8 3. SQL Syntax Create, Drop, Modify table Create table Customer ( id number, name varchar2(20), address varchar2(50), phone varchar2(20), birth_date date ); Alter table Customer add ( varchar2(30) ); Alter table account drop column ; Drop table Customer; 8

9 3. SQL Syntax Insert data into table Create table test1 ( id number, name varchar2(20), salary number); Insert into test1 values ( 5, Ming, 5000); -- values will mapping to the table columns accordingly Insert into test1 ( id, name, salary) values ( 8, Zhang, 8000); -- values will mapping to the columns specified above Insert into test1 (salary, id) values ( 7000, 6); -- Column NAME is not specified, will get a NULL value commit; rollback; Select * from test1; 9

10 3. SQL Syntax Delete data from table Select * from test1; Delete Test1 Where ID = 5; commit; Delete Test1; rollback; 10

11 3. SQL Syntax UPDATE data from table Select * from test1; Update Test1 set salary = 5588 where ID = 5; commit; Update Test1 set salary = 5588; rollback; 11

12 3. SQL Syntax Select data from table Select * from Emp; Select Empno, Ename, Job, Sal From Emp Where Sal > 2000 Order by Ename; 12

13 3. SQL Syntax Select data from table: Select Clause -- Display all column from data source Select * from Emp; Select Empno, ename, mgr, job, sal, comm from Emp; -- Display 1 column from data source Select Ename From Emp; -- Display 4 columns, column name separated by, Select Empno, Ename, Job, Sal From Emp; -- Display data from different tables. -- Put table name before column name to avoid confusion Select Emp. Ename, Dept.Loc From Emp, Dept where Emp.deptno = Dept.deptno; 13

14 3. SQL Syntax Select data from table: FROM Clause Select * From Emp; -- Separate table name with comma Select Emp. Ename, Dept.Loc From Emp, Dept where Emp.deptno = Dept.deptno; -- Separate table name with comma. Using table alias Select E.Ename, D.Loc From Emp E, Dept D where E.deptno = D.deptno; 14

15 3. SQL Syntax Select data from table: WHERE Clause Select * From Emp Where condition; ID = 5 ID >=5 ID < 10 Name = Zhang Name > Zhang Name <= Zhang ID in ( 5, 8, 10) ID NOT in ( 5, 8, 10) Name like Zh% -- % any number of character Name like _h% -- _ a single character Name between A and C ID between 5 and 10 Name in ( Zhang, Wang, Li ) ID NOT between 5 and 10 Birth_date > 01-JAN-2001 Between date1 and date2 15

16 3. SQL Syntax Select data from table: ORDER BY Clause -- You can sort the selected data by order of ANY column(s) in the source table(s). -- Columns are separated by comma (,) -- SORT can be ASC (Ascending) or DESC (descending) Default is ASC -- If sorted column is in the select clause, you can use 1 or 2.. To represent them Select Empno, Ename, Sal From Emp Where condition1 Order by 1,3, hire_date; Select Empno, Ename, Sal From Emp Where condition1 Order by sal desc; Select.. From Table_a, Table_b Where join_condition Order By table_a.column asc, table_b.column desc; 16

17 4. Pre-Defined Function Distinct Number Function Character Function Data Function Conversion Function Misc. Function 17

18 4. Pre-Defined Function Distinct, or Unique Select deptno from Dept; Select Distinct Deptno From Dept; 18

19 4. Pre-Defined Function Number Function Single Row Function + - x / abs power sign Round Trunc Mod greatest least Group Function Max Min Avg Sum count Using DUAL Table: Select Round(123.46, -1) From Dual; 19

20 4. Pre-Defined Function Character Function upper, Lower concat ltrim rtrim trim lpad rpad length substr instr replace 20

21 4. Pre-Defined Function Date Function to_char to_date round trunc add_month Sysdate Date Format: YYYY YY RRRR RR Month MM DD D DAY HH24 MI SS 21

22 4. Pre-Defined Function Conversion Function to_char to_date to_number 22

23 4. Pre-Defined Function Other Functions NVL Replace Decode Case 23

24 5. Advanced query Sub-query, Query with Group function Set operation Group and Set Examples Pseudo column Query using decode and case Using PL/SQL for complex query 24

25 5. Advanced query Sub-query, Query with Group function Select * From Emp; Select max(sal) from emp; Select ename, max(sal) from emp group by ename; Select ename, sal From emp Where sal = (select max(sal) from emp); Select a.ename, b.loc From emp a, dept b Where a.deptno = b.deptno; Select a.ename, (select loc from dept where deptno= a.deptno) Loc From emp a; 25

26 5. Advanced query Sub-query, Query with Group function Select ename, sal From emp Where sal = (select max(sal) from emp); 2 nd highest salary Select max( sal ) From emp Where sal! = (select max(sal) from emp); Select ename, sal From emp Where sal = ( Select max( sal ) From emp Where sal! = (select max(sal) from emp) ); 26

27 5. Advanced query Group Query Select sum(sal) From emp Where deptno = 10; Select deptno, sum(sal) from emp -- Group by deptno Order by deptno; Select deptno, sum(sal) from emp Where Group by deptno having sum(sal) > 1000 Order by deptno; 27

28 5. Advanced query Set operation Union All, Union, Minus, Intersect A = ( 1, 2, 5 ) B = ( 1, 4 ) A Union All B = ( 1, 2, 5, 1, 4 ) A Union B = ( 1, 2, 4, 5 ) A Minus B = ( 2, 5 ) B Minus A = ( 4 ) A Intersect B = ( 1 ) When do set operation with 2 tables: 1. The number of columns should be the same 2. Column data type must be the same. May need to use to_char function. Example: Find the change ( table_a and its backup) 28

29 5. Advanced query Some Examples -- Top n Select * From ( select * from emp order by sal) a where rownum <= 5; 29

30 5. Advanced query Pseudo column (1): Rownum Select * from emp where rownum < 3; Select * from emp where rownum < 3 order by 1; Select * from emp where rownum = 3; Select * from emp where rownum <= 3 Minus Select * from emp where rownum <= 2; Select b.* from ( Select rownum xx, a.* from emp a ) b where b.xx =5; 30

31 5. Advanced query Pseudo column (2): Rowid Every record in every table has its own address - ROWID Select ename, sal from dept; Select rowid, ename, sal from emp; 31

32 5. Advanced query Pseudo column (2): Rowid Example: Duplicate records 1. How you know there is a duplicate count(id) diff from count(distinct id) 2. How to identify which one have duplicate having count(id) > 1 3. Delete duplicate records from table. Insert into dept Select * from dept ; Select Distinct * from dept; Delete Dept a Where rowid!= ( select max(rowid) from dept where deptno = a.deptno); 32

33 5. Advanced query Query using decode Create table exam_score ( Name varchar2(30), Grade number -- 1 to 5 ); Insert into exam_score values ('Zhang', 5); Insert into exam_score values ('Li', 4); Insert into exam_score values ('wang', 2); COMMIT; Select name, grade, decode(grade, 5, 'Excellent', 4, 'Very Good', 3, 'Good', 2, 'Work harder', 1, 'Go home') Suggestion From Exam_Score; 33

34 5. Advanced query Query using case Delete Exam_Score; Commit; Insert into Exam_Score values ('Zhang', 95); Insert into Exam_Score values ('Li', 88); Insert into Exam_Score values ('Wang', 55); Select name, grade, case when grade >= 90 then 'Excellent' when grade between 80 and 89 then 'Very Good' when grade between 70 and 79 then 'Good' when grade < 70 End comments From Exam_Score then 'be careful' 34

35 6. Join Where the Join comes from Database design Relation between tables ERD Types of Join Equijoin Non-equijoin Inner join Outer join Self join 35

36 6. Join: Type Cartesian Products (No join condition) Select a.ename, b.loc From Emp a, Dept b; Equijoin ( using equal to join) Select a.ename, b.loc From Emp a, Dept b Where a.deptno = b.deptno and a.sal between 1000 and 4000; Non-equijoin ( Using non-equal to join) Select a.ename, b.loc From Emp a, Dept b Where a.deptno = b.deptno and a.f1 > b.f2; Insert into DEPT ( 88, 'East', HuNan'); Commit; Inner join Return a row only join value is not null Select b.loc, a.ename From emp a, dept b Where b.deptno = a.deptno; Outer join Return a row even the value is null Select b.loc, a.ename From emp a, dept b Where b.deptno(+) = a.deptno; Self Join Select a.ename, b.ename manager From Emp a, emp b Where a.mgr = b.empno; 36

37 7. Create table, Insert, Delete, Update Create table with constraints Create from query Insert Truncate and Delete Update 37

38 7. Create table, Insert, Delete, Update Create table with constraints Constraints: Not Null, Null, Primary Key Forein Key Check Create Table Account ( Account_No number primary key, Cust_name varchar2(30) Not null, Phone varchar2(20), Sex varchar2(1) check ( sex in ('F', 'M') ) ); Create table from query Useful to create backup, and temp table Create table Emp2 as select * from emp; Create table Emp2 as select * from emp where 1=2; Create table Emp_Loc as Select a.ename, b.loc From emp a, dept b where a.deptno = b.deptno; Drop Table Account; Alter table account add varchar2(20); Alter table account drop column ; Select constraint_name, constraint_type from user_constraints where table_name = 'ACCOUNT'; Select constraint_name, column_name from user_cons_columns where table_name = 'ACCOUNT'; 38

39 7. Create table, Insert, Delete, Update Insert Create table Emp_Loc ( employee_name varchar2(20), Work_Location varchar2(20) ); Insert into Emp_Loc Select a.ename, b.loc From emp a, dept b where a.deptno = b.deptno; 39

40 7. Create table, Insert, Delete, Update Truncate and Delete 1. Delete is the opposite of insert 2. How insert, delete, and truncate work Create table emp2 as select * from emp; Delete emp2 where deptno = 10; Delete emp2; Rollback; Truncate table emp2; -- No chance to rollback 40

41 7. Create table, Insert, Delete, Update Update Create table Loc_Change ( dept_no number, new_loc varchar2(20) ); Insert into Loc_Change values ( 10, 'Wuhan'); Insert into Loc_Change values ( 20, 'Jinan'); Insert into Loc_Change values ( 30, 'Beijing'); Insert into Loc_Change values ( 40, 'Hunan'); Commit; Create table Dept2 as Select * from Dept; Select * from dept2; Update Dept2 Set Loc = 'ChangSha' Where Deptno = 40; Update Dept2 D Set D.Loc = ( select L.new_loc from Loc_Change L where L.dept_no = D.deptno ) where D.deptno in (select dept_no from loc_change) 41

42 8. Create view, sequence and synonym Create View Syntax Create or replace view Emp_v1 As Select a.ename, a.job, b.loc From emp a, Dept b where a.deptno = b.deptno; Create or replace view Emp_v2 As Select a.ename, a.sal, a.hiredate From emp a; Select * from emp_v1 where ename = 'Mike'; Select * from emp_v2 where ename = 'Mike'; Why View 1. For the data safety View itself is a SELECT statement with all the necessary join conditions. By using view, user can still do the query, but not directly access the source table. 2. For the convenience of user The Complex selection or business rules are hided under the view, Sequence Create sequence Order_Seq start with increment by 1; Insert into Order (order_no, amount) Values ( order_seq.nextval, 500); 42

43 8. Create view, sequence and synonym Synonym User Demo owns table Test_Table, but other users want to access it. Create user demo, logon as demo, create a table, and insert some data -- Log on as scott -- To access other's table, need to put owner's name before table name Select * from demo.test_table; -- Logon as Demo Grant select on test_table to scott; -- Log on as scott select * from demo.test_table; Create synonym test_table for demo.test_table; select * from demo.test_table; 43

44 9. Performance issue How to improve performance How index works Index rearranged the data in order, along with the rowid Use or not use the index Select * From Emp Where ename = 'MIKE'; Create index, composite index Create index emp_ind1 on Emp ( ename ); Create index emp_ind2 on Emp ( ename, Sal ); Select Ename, Sal From Emp Where ename = 'MIKe'; Select Ename, Sal From Emp Where UPPER(ename) = 'MIKE'; 44

45 10. Security and safety Security Account management Create user Demo identified by 1234; Grant connect, resource to demo; Alter user account lock/unlock; Grant/Revoke privilege Create user Demo identified by 1234; Grant connect, resource to demo; Grant select on emp to demo; Grant ALL on Dept to demo; Using view Create a view for a specific table, then grant the select privilege of the view, instead the table, to some users. So by controlling the columns in the view, we control what user can see. Using PL/SQL trigger Write a PL/SQL trigger, when user insert, or update, or delete, raise an error, or tracking what user doing. 45

46 10. Security and safety Safety Work on temp tables or backup the source data. Loosing data by accident, such as unwanted delete or update, or drop table,may cause lots of trouble for you, big lose for the company. You may put your job at risk. To prevent this kind of accident, you may work on temp table ( copy from real table); Or work on the real table, but back up the table first. To grantee the database safety, usually we have 3 Databases: 1. DVLP Database: For developing new program 2. TEST Database: For testing program, including performance 3. PROD Database: For Real Business only. 46

47 12. Data Dictionary 3 Prefixes: USER_, ALL_, DBA_ For example, USER_TABLES store info for tables which the log on user is the OWNER ALL_TABLES store info for tables of ALL users DBA_TABLES store info for tables of ALL users AND database internal tables DICT, User_objects User_tables, User_tab_columns User_Index, User_ind_columns User_Views User_Sequence 47

48 12. Data Dictionary DICT, or Dictionary All the data dictionary names DESC DICT Select table_name from Dict; User_objects A good habit to query an unknown table is do DESC and select count(*) first Select owner, object_type, object_name, created, last_ddl_time From ALL_Objects where object_name = 'EMP'; 48

49 12. Data Dictionary User_tables, User_tab_columns Select table_name, column_id, column_name, data_type From User_tab_columns Where table_name = 'DEPT' order by column_id; DESC does the same thing User_Index, User_ind_columns Select index_name, column_position, column_name From User_ind_columns where table_name = 'EMP' Knowing which column is indexed and its index position is very important to understand the performance of a query. 49

50 12. Data Dictionary User_Views DESC User_view -- Don't forget following command -- when query data with -- LONG data type Set Long Select text from All_view where view_name = 'EMP_V'; User_Sequence Create Sequence ss1 Start with increment by 1 select sequence_name, min_value, max_value, increment_by from User_sequences 50

51 13. SQL Plus command and Script Using SQL Plus script to generate SQL script Select Ename from Emp; Select Ename ' is my friend.' from Emp; Select ' Select count(*) from ' table_name ';' From User_tables; Spool new_script.txt Select ' Select count(*) from ' table_name ';' From User_tables; Spool off Spool new_script.txt Select ' Select ' ' '' ' table_name ' '' ' ',' count(*) from ' table_name ';' From User_tables; Spool off 51

52 Oracle PL/SQL January 9, 2007 Dai Mu-Hong Copyright

53 1. Introduction SQL vs. PL/SQL SQL: A command or statement to 1. Query ( select ) 2. DML. Manipulate ( insert, update, delete ) 3. DDL. Create database objects ( table, view, index,..) PL/SQL: Procedural programming extention of SQL Developed and used by Oracle only PL/SQL = SQL + Loop, Condition, Error handling 53

54 1. Introduction SQL vs. PL/SQL 3 Basic Types of PL/SQL program: Procedure: Return none or multiple values Function: Return one value Trigger: An event driven program Package is a group of procedures and functions organized together for easier management and higher performance 54

55 2. Components of PL/SQL program 1. Declare - Use this part to declare all the variables with their datatype and default values used in the program. If no variables used in the program, this section can be omitted. 2. Begin - Start of the execution part 3. Exception - In case of run time errors occured, program enter this section automatically. You can write codes here to handle the errors. This section may be omitted. In this case, the program will stop to run and error out when there is a run time error. 4. End - End of Program - Do not forget to put a dash / at the begining of next line, as the final end of the program. 55

56 Why need a - / - at the end of the program? Declare Begin For Loop Declare Begin Exception End; End Loop; Exception End; / 56

57 2. Components of PL/SQL program A Sample Program CITY table has 2 coumns, ID and Name. For ID (5) and name (changsha), the program: 1. Query the table with ID 5 2. If ID already exists, do Update Else, do a insert DECLARE v_cnt number; v_id number; v_name varchar2(10); BEGIN v_id := 5; v_status := 'changsha'; IF v_cnt > 0 Then ELSE UPDATE CITY SET name = v_name WHERE id = v_id; INSERT INTO CITY ( id, name ) values (v_id, v_name); END IF; COMMIT; Exception when others then null; END; / SELECT count(*) INTO v_cnt FROM CITY WHERE ID = v_id; test21.sql 57

58 2. Components of PL/SQL program Varable datatype in Declare Section 1. Number Number(4) Number(5,2) Integer Binary_integer v_id number; char(5) varchar2(20) v_name varchar2(30); Date v_entry_date Date; Boolean v_pass Boolean; 2. %type v_emp_name EMP.ename%type; %rowtype v_emp_rec EMP%rowtype; 3. Cursor Cursor c_emp is select * from emp; 4. Exception E_1 Exception; 5. Self defined type Record or array 58

59 2. Components of PL/SQL program Assignment V_ID := 5; V_Name := 'Chang Sha'; V_Phone := ' '; V_Phone_area_code := substr ( v_phone, 1, 4); V_Start_Date := Sysdate; V_Start_date := to_date('1/2/2007','mm/dd/yyyy'); V_Full_Name := v_last_name v_first_name; V_Pass := TRUE; 1. Select count(*) Into v_cnt From emp Where deptno = v_deptno; 2. Select * Into R_Emp From emp where deptno = v_deptno; v_empno := R_Emp.empno; For direct asignment, using := For asignment with Select, using INTO For comparism, equal =, Not Eaqual!= or <> 59

60 2. Components of PL/SQL program Logic Control IF IF x=5 Then Insert.. Elsif... Else Update. End If; WHILE X := 1; While x < 5 Loop Do something; X := X + 1; End Loop; GOTO IF x=5 Then GOTO some_where; End If;... <<some_where>> At least one line here... CASE A. Case X when 5 then y := 50; B. when 8 then y := 1000; else y := 0; End case; Case when x=5 then y := 50; when x>5 then y := 1000; Else y := 0; End case; 60

61 2. Components of PL/SQL program LOOP 1. LOOP... Exit when... End Loop; 3. While x < 5 LOOP... x := x + 1; End Loop; 2. For k in 1..5 LOOP... End Loop; c_emp is a cursor For v_emp in c_emp Loop Insert Into... values ( v_emp.sal,...); End Loop; 61

62 2. Components of PL/SQL program Exception Declare v_ename emp.ename%type; v_sal number; -- e1 exception; -- e2 exception; Begin select ename into v_ename from emp where enmno = '123456'; select sal into v_sal from emp where deptno = 10; 1. Without exception part 2. With exception part use when others syntax in exception handling. 3. Handle exception for each select statement 4. Raise exception in the select, then pass the exception to the main Exception part --Exception End; / 62

63 Exception When no_data_found then V_msg := 'no company for id ' TO_CHAR (v_id); V_err := SQLCODE; V_prog := 'fixdebt'; INSERT INTO errlog VALUES (V_err,v_msg,v_prog,SYSDATE,user); When others then V_err := SQLCODE; V_msg := SQLERRM; V_prog := 'fixdebt'; INSERT INTO errlog VALUES (V_err,v_msg,v_prog,SYSDATE,user); Raise; 63

64 3. Procedure and Function Anonymous Procedure 1. Declare... Begin... Exception... End; / Save above codes as Test.sql This file is saved in the client hard drive, not in the Database. Runing this file is running the code inside the file. Stored Procedure 2. Create or replace procedure T1 as... Begin... Exception... End; / Save above codes as Test.sql, in the hard drive. Runing this file only compile and create a procedure named T1 in the database, NOT running the code inside the file. To run the codes, we need to execute the procedure T1. SQL> Exec T1 64

65 3. Procedure and Function Pass Parameters Anonymous Procedure 1. Declare Begin x number; x := &1;... Exception... End; / Save above codes as Test.sql Stored Procedure 2. Create or replace procedure T1 ( p1 in number, p2 in varchar2 ) as... Begin... Exception... End; / Save above codes as Test.sql SQL> Exec T1(5, 'Mike') 65

66 3. Procedure and Function Run/Call Stored procedure Procedure T1: Create or replace procedure T1 ( p1 in number, p2 in number, p3 out number ) as Begin End; / p3 := p1 + p2; Save above codes as P_Test1.sql to create T1 SQL> Exec T1(5, 'Mike') Procedure T2: Create or replace procedure T2 (x number, y number) as Z number; Begin T1(X, Y, Z); dbms_output.put_line ('The sum of ' x ' and ' Y ' is ' Z); End; / Save above codes as P_Test2.sql to create T2 SQL> Exec T2(5, 8) 66

67 3. Procedure and Function Run/Call Stored function Procedure T1: Create or replace function T1 ( p1 in number, p2 in number -- p3 out number ) Return number as Begin End; / return( p1 + p2); Save above codes as P_Test1.sql to create T1 SQL> select T1(3,5) from dual; Procedure T2: Create or replace procedure T2 (x number, y number) as Z number; Begin Z := T1(x,y); dbms_output.put_line ('The sum of ' x ' and ' Y ' is ' Z); End; / Save above codes as P_Test2.sql to create T2 SQL> Exec T2(5, 8) 67

68 3. Procedure and Function Run/Call Stored Function Function F1: Create or replace function F1 (p1 in varchar2) Return varchar2 as v_in varchar2(30) := p1; v_out varchar2(30); Begin while length(v_in) > 0 Loop v_out := v_out substr(v_in, length(v_in),1); v_in := substr(v_in, 1, length(v_in)-1); End Loop; Return v_out; End; / Save as F_Test1.sql, to create function F1 After Function F1 created, we may use it in SQL or programs. Run/Call Function F1 A. In SQL statement SQL> select f1('abcd') from dual; SQL> select dname, substr(f1(dname),1,20) from dept; B. Call from procedure or function Set serveroutput on Declare Z varchar2(20); Begin Z:= F1('HuNan University'); dbms_output.put_line( Z); End; / Save above codes as Test3.sql 68

69 3. Procedure and Function Using Cursor Procedure T5: Set serveroutput on size Declare Cursor c1 is select * from Emp; Begin For v1 in c1 loop End; / dbms_output.put_line (v1.ename ' makes a salary of ' v1.sal); Save above codes as P_Test3.sql 69

70 3. Procedure and Function Exception Declare Begin v_ename emp.ename%type; v_sal number; -- e1 exception; -- e2 exception; select ename into v_ename from emp where enmno = '123456'; 1. Without exception part 2. With exception part use when others syntax in exception handling. 3. Handle exception for each select statement 4. Raise exception in the select, then pass the exception to the main Exception part select sal into v_sal from emp where deptno = 10; --Exception End; / 70

71 3. Procedure and Function Exception Procedure T6: handle exception while continue to process Declare Begin For Loop Declare Begin Exception End; End Loop; Exception End; / 71

72 3. Procedure and Function Examples: 1a. Single For Loop Create or Replace procedure P1 (p_in number) as v_line varchar2(20):= '*'; Begin For i in 1..p_in Loop End; / v_line := Rpad(v_line, i, '*'); DBMS_Output.put_line(v_line); End Loop; SQL> Set Serveroutput on SQL> Exec p1(6) 72

73 3. Procedure and Function Examples: 1b. Double For Loop Create or Replace procedure P99 as v_line varchar2(150); z varchar2(20); Begin For i in 1..9 Loop v_line := NULL; For j in 1..9 Loop End; / z := i '*' j '=' i*j; z := rpad(z, 7); v_line := v_line ' ' z; End Loop; -- j loop DBMS_output.put_line(v_line); End Loop; -- i loop SQL> Set Serveroutput on SQL> Exec p99 73

74 3. Procedure and Function Examples: 2. Prime Number Create or Replace function Is_Prime (p_in number) Return Boolean as v_prime boolean := true; Begin If P_in in (1,2,3) Then v_prime := true; goto print_section; End if; For i in 2.. round(p_in/2) Loop if mod(p_in, i) = 0 Then v_prime := false; exit; end if; End Loop; <<print_section>> return v_prime; End; / Create or Replace procedure G_Guess (p_in number) as j number; v_result varchar2(100) := null; Begin If is_prime(p_in) then v_result := P_in ' itself is a prime'; goto print_result; End If; For i in 1..p_in/2 Loop j := p_in - i; if is_prime(i) and is_prime(j) Then v_result :=p_in ' = ' i ' + ' j; Exit; End if; End Loop; <<print_result>> If v_result is not null Then dbms_output.put_line (v_result); else dbms_output.put_line ('G Guess fail.'); end if; End; / 74

75 3. Procedure and Function Tracing and Debugging Find/Correct Compiling Syntax errors SQL> show error Find/Correct Run time error Using a loc variable, then Display loc at exception section Using GOTO to bypass some parts of the program 75

76 4. Trigger A unique Implementation of PL/SQL Stored in DB, but not stored procedure or functions Event Driven Perform some kind of action in the database Purpose of Trigger Maintain complex integrity constraints Auditing Automatically signaling other programs when changes are made to a table 76

77 4. Trigger Types of Triggers A. System Trigger on system events, such as Logon and logoff on DDL, such as create database objects B. Database Trigger Fired by a DML statement, such as Insert, update, or delete 77

78 4. Trigger Example of System Trigger Create table Test9 ( User_name varchar2(20), Log_Time date ); Create or replace trigger T9 after logon on schema -- Before logoff on schema when (user = 'SCOTT') Begin Insert into Test9 values (user, sysdate); End; / 78

79 4. Trigger Example of Database Trigger (1) Create Table Test_10 (Greeting varchar2(30)); Create or Replace Trigger T_10 Before Insert on Test_10 For Each Row Declare Begin IF upper(:new.greeting) like '%BAD%' then :new.greeting := replace(upper(:new.greeting), 'BAD', 'GOOD'); :new.greeting := initcap(:new.greeting); End IF; End; / 79

80 4. Trigger Example of Database Trigger (1B) Create Table test_10 (Greeting varchar2(30)); Create Table Good_Bad (B_Word varchar2(20), G_Word varchar2(20)); Insert into Good_Bad values ('BAD', 'GOOD' ); Insert into Good_Bad values ('HATE', 'LOVE' ); Insert into Good_Bad values ('SAD', 'HAPPY'); COMMIT; Create or Replace Trigger T_10B Before Insert on Test_10 For Each Row Declare Cursor c1 is select * from Good_Bad; Begin For v1 in c1 Loop :new.greeting := replace(upper(:new.greeting), v1.b_word, v1.g_word); :new.greeting := initcap(:new.greeting); End Loop; End; / 80

81 4. Trigger Example of Database Trigger (2) Create Table test_10 (Greeting varchar2(30)); Create Table test_11 (username varchar2(10), insert_time date, comment varchar2(50)); Create or Replace Trigger T_11 After Insert on Test_10 For Each Row Begin Insert into Test_11 values (user, sysdate, 'Inserted value is: ' :new.greeting); End; / 81

82 4. Trigger Example of Database Trigger (3) Create Table Account ( Cust_name varchar2(20), account# varchar2(10), balance number, interest number ); Create Table Account_Audit ( account# varchar2(10), username varchar2(10), upd_time date, old_balance number, new_balance number, old_interest number, new_interest number ); Create or Replace Trigger T_12 After Update on Account For Each Row Begin Insert into Account_Audit values ( :old.account#, user, sysdate, :old.balance, :new.balance, :old.interest, :new.interest ); End; / 82