1

JumpStart PL/SQL

Wang Hao

2

Outline

• PL/SQL Programming

• SQL*Plus and SQL commands

3

PL/SQL Programming

• PL/SQL is an extension to SQL with design features of programming languages.

• Data manipulation and query statements of SQL are included within procedural units of code.

4

Benefits of PL/SQL

• Integration of applications, shared library and Oracle server.

• Improve performance.

application Other DBMSsSQL

applicationOracle with PL/SQL

IF … THEN SQL ELSE SQL END IF;

5

PL/SQL Block Structure

• DECLARE –Optional– Variables, cursors, uer-define exceptions

• BEGIN – Mandatory– SQL statements– PL/SQL statements

• EXCEPTION – Optional– Actions to perform when errors occur

• END; - Mandatory

6

PL/SQL Block Structure(1)

DECLAREv_variable VARCHAR2(5);

BEGINSELECT column_name

INTO v_variable FROM table_nameEXCEPTION … WHEN exception_name THENEND;

7

Block TypesProcedure

PROCEDURE name IS

BEGIN

-- statements

[EXCETPION]

END;

Function

FUNCTION name RETURN datatype IS

BEGIN

-- statements RETURN value;[EXCETPION]

END;

[DECLARE]

BEGIN

-- statements

[EXCETPION]

END;

8

Program Constructs

• Anonymous Block– Unnamed PL/SQL block that is embedded within an

application or is issued interactively

• Stored procedure or functionNamed PL/SQL block stored in Oracle Server that can accept parameters and be invoked repeatedly by name.

• PackageNamed PL/SQL module that groups related procedures, functions and identifiers. Stored in Oracle server or Oracle Developer components – for example, Forms.

9

Handling Variables in PL/SQL

• Declare and initialize variables in the declaration section.

• Assign new values to variables in the executable section.

• Pass values into PL/SQL blocks through parameters.

• View results through output variables.

10

Types of PL/SQL Variables

• Scalar– BOOLEAN, DATE, NUMBER, VARCHAR2

• Composite– Such as records.

• Reference– Pointers

• LOB (large objects)– Used to hold large objects such as images.

• Non-PL/SQL variables: bind and host variables.

11

Declaring PL/SQL Variables

• Examples:Declare

v_hiredate DATEv_deptno NUMBER(2) NOT NULL :=10;v_location VARCHAR(13) := ‘New York’;v_tax_rate NUMBER(3,2) := 3.0;c_comm CONSTANT NUMBER := 1400;

• Guidelines:– Follow naming conventions.– Initialize variables designated as NOT NULL.– Declare at most one identifier per line.

12

Base Scalar Datatypes• VARCHAR2(maximum_length)

– No default size; max = 32767 bytes

• NUMBER[(precision, scale)]– For fixed and floating numbers.

• CHAR[(maximum_length)]– For fixed-length character string. Default to 1.

• BOOLEAN– TURE, FALSE, or NULL

• BINARY_INTEGER– Base type of integers between -2,147,483,647 and 2,147,483,647.

• PLS_INTEGER– Same range as BINARY_INTEGER but requires less storage and are faster

than NUMBER and BINARY_INTEGER values.

13

Declaring Variables with the % TYPE attribute

• Declare a variable according to – A database column definition– Another previously declared variables.

• Prefix % TYPE

• Examples:v_ename emp.ename%TYPE;

v_balance NUMBER(7,2);

v_min_balance v_balance%TYPE := 10;

14

PL/SQL Block Syntax and Guidelines

• Statements can continue over several lines.• Identifiers

– Can contain up to 30 characters.– Must begin with alphabetic character.

• Literals– Enclosed in single quotation marks.

• A PL/SQL block is terminated by a slash / on a line by itself.

• Commenting code– Single-line comments with two dashes (--).– Place multi-line comments between /* and */

15

Operators

• Arithmetic+ , -, *, / , **,

• Comparison=, <, >, >=, <=, !=, IS NULL, LIKE, BETWEEN, IN

• Assignment:=

• Statement terminator;

• String concatenation||

• LogicalNOTG, AND , OR

16

SQL Statements in PL/SQL• Extract a row of data from the database by using the

SELECT command. Only a single set of values can be returned.

• Make changes to rows in the database by using DML commands. (INSERT, UPDATE, DELETE).

• Control a transaction with the COMMIT, ROLLBACK or SAVEPOINT command.

• Determine DML outcome with implicit cursors.• Does not support DDL (CREATE TABLE, ALTER

TABLE, or DROP TABLE) and DCL (GRANT, REVOKE)

17

SELECT Statements in PL/SQL

• Retrieve data from the database with SELECT.• Example:DECLARE

v_dept_no NUMBER(2);v_loc VARCHAR2(15);

BEGINSELECT deptno, locINTO v_deptno, v_locFROM deptWHERE dname=‘SALES’;

END;

18

Manipulating Data Using PL/SQL

• INSERTBEGININSERT INTO emp(empno, ename, job, deptno)VALUES (empno_sequence.NEXTVAL, ‘Jack’, ‘CTO’, 10);

END;

• UPDATEBEGIN

UPDATE empSET sal = sal + 10; WHERE job = ‘ANALYST’;

END;

19

Manipulating Data Using PL/SQL

• DELETEBEGIN

DELETE FROM emp

WHERE name = ‘JACK’;

END;

20

Writing Control Structures

• Conditional IF statements.IF v_dept_no = 10 THEN

v_bonus := 5000;

ELSIF v_dept_no=20 THEN

v_bonus := 7500;

ELSE

v_bonus := 2000;

END IF;

21

Writing Control Structures• Iterative control: loop statements

– Basic loop– FOR loop– WHIE loop

• Basic loopBEGIN

LOOPINSERT INTO item(ordid, itemid)VALUES (610, v_counter);v_counter := counter + 1;EXIT WHEN v_counter > 10;

END LOOP;COMMIT;

END;

22

Writing Control Structures• FOR loop

BEGINFOR i IN 1..100 LOOP……END LOOP;

END;

• WHILE loopBEGINWHILE i <= 100 LOOP

……END LOOP;

END;

• Nested loop is allowed.

23

SQL Cursor

• A cursor is a private SQL work area. Each SQL statement executed by the Oracle Server has an individual cursor associated with it.

• There are two types of cursors:– Implicit cursors– Explicit cursors

• The Oracle Server uses implicit cursors to parse and execute your SQL statements.

• Explicit cursors are explicitly declared by the programmer.

24

SQL Cursor Attributes• Using SQL cursor attributes, you can test

the outcome of your SQL statements.SQL%ROWCOUNT Number of rows affected by the most

recent SQL statement. (an integer value).

SQL%FOUND Boolean attribute that evaluates to TRUE if the most recent SQL statement affects one or more rows.

SQL%NOTFOUND Boolean attribute that evaluates to TRUE if the most recent SQL statement does not affect any row.

SQL%ISOPEN Always evaluates to FALSE because PL/SQL closes implicit cursors immediately after they are executed.

25

Cursor

Writing Explicit Cursors

• Use explicit cursors to individually process each row returned by a multi-row SELECT statement.

Active Set

7369 SMITH CLERK

7430 JONES MANAGER

7788 SCOTT ANALYST

7789 JACK CTO

Current Row

26

Writing Explicit Cursors: ExampleDECLARE

v_empno emp.empno%TYPE;v_ename emp.ename%TYPE;CURSOR emp_cursor IS

SELECT empno, enameFROM emp;

BEGINOPEN emp_cursor;LOOP

FETCH emp_cursor INTO v_empno, v_ename;EXIT WHEN emp_cursor%NOTFOUND;……

END LOOP;CLOSE emp_cursor;

27

Cursors with Parameters

• Example: pass the department number and job title to the WHERE clause.

DECALRECURSOR emp_cursor(p_deptno NUMBER, p_job VARCHAR2) IS

SELECT empno, enameFROM empWHERE deptno = v_deptno AND job = v_job;

BEGINOPEN emp_cursor(10, ‘CLERK’);

……

28

Cursors with Subqueries

DECALRE

CURSOR my_cursor IS

SELECT t1.deptno, t1.dname, t2.STAFF

FROMdept t1, (SELECT deptno,

count(*) STAFF

FROM emp

GROUP BY deptno) t2

WHERE t1.deptno = t2.deptno

AND t2.STAFF >= 5;

29

Using Arrays• Item type: VARRAY (short for Variable-size arrays). • A varray can have only one dimension and must be indexed by

integers.• A varray has a maximum size.• Example:DECALRE

TYPE list IS VARRAY(25) of NUMBER(3);v1 v_list;

BEGINFOR i IN 1..25

v1(i) := 1;END LOOP;

END;

30

Subprograms

• Subprograms are named PL/SQL blocks that can take parameters and be invoked. PL/SQL has two types of subprograms called procedures and functions.

• Example: a procedure named debit_account, which debits a bank account:

31

PROCEDURE debit_account (acct_id INTEGER, amount REAL) IS old_balance REAL; new_balance REAL; overdrawn EXCEPTION;BEGIN SELECT bal INTO old_balance FROM accts WHERE acct_no = acct_id; new_balance := old_balance - amount; IF new_balance < 0 THEN RAISE overdrawn; ELSE UPDATE accts SET bal = new_balance WHERE acct_no = acct_id; END IF;EXCEPTION WHEN overdrawn THEN ...END debit_account;

32

Writing Functions• Consider the function sal_ok, which determines if a

salary is out of range:

FUNCTION sal_ok (salary REAL, title VARCHAR2) RETURN BOOLEAN IS

min_sal REAL; max_sal REAL;BEGIN SELECT losal, hisal INTO min_sal, max_sal FROM

sals WHERE job = title; RETURN (salary >= min_sal) AND (salary <=

max_sal);END sal_ok;

33

Parameter Modes• IN mode (the default)

– passes values to a subprogram.– actual parameter is passed by reference (a pointer to the

value is passed in)

• OUT mode (must be specified)– returns values to the caller.– actual parameter is passed by value (a copy of the value is

passed out) unless NOCOPY is specified

• IN OUT mode (must be specified)– passes initial values to a subprogram and returns updated

values to the caller.– actual parameter is passed by value.

34

Declaring Subprograms

• You can declare subprograms in any PL/SQL block, subprogram, or package. But, you must declare subprograms at the end of a declarative section after all other program items.

• PL/SQL requires that you declare an identifier before using it. Therefore, you must declare a subprogram before calling it.

35

Packaging Subprograms

• You can group logically related subprograms in a packages, which is stored in the database.

• Packaged subprograms can be shared by many applications, while hiding implementation details.

• Package spec: declares the subprograms, and • Package body: implements the subprograms.• Example:

36

• Creating Package Spec:CREATE OR REPLACE PACKAGE emp_actions AS PROCEDURE hire_employee (emp_id INTEGER, name VARCHAR2, ...);

PROCEDURE fire_employee (emp_id INTEGER);

PROCEDURE raise_salary (emp_id INTEGER, amount REAL);

...END emp_actions;

• Creating Package Body:

37

CREATE OR REPALCE PACKAGE BODY emp_actions AS PROCEDURE hire_employee (emp_id INTEGER, name VARCHAR2, ...) IS

BEGIN ... INSERT INTO emp VALUES (emp_id, name, ...); END hire_employee;

PROCEDURE fire_employee (emp_id INTEGER) IS BEGIN DELETE FROM emp WHERE empno = emp_id; END fire_employee;

PROCEDURE raise_salary (emp_id INTEGER, amount REAL) IS BEGIN UPDATE emp SET sal = sal + amount WHERE empno = emp_id; END raise_salary; ...END emp_actions;

38

Packaging Subprograms

• You can define subprograms in a package body without declaring their specs in the package spec. However, such subprograms can be called only from inside the package.

• Guidelines:– Put package spec and body in separate files.– Compile package spec first before compiling

package body.

39

Referencing Package Contents

• To reference the types, items, subprograms, and call specs declared within a package spec, use dot notation, as follows: – package_name.type_name– package_name.item_name– package_name.subprogram_name– package_name.call_spec_name

• Example:SQL> CALL emp_actions.hire_employee('TATE',

'CLERK', ...);

40

Oracle Packages: DBMS_OUTPUT

• Package DBMS_OUTPUT enables you to display output from PL/SQL blocks and subprograms, which makes it easier to test and debug them.

• You display the information by calling the procedure get_line or by setting SERVEROUTPUT ON in SQL*Plus.

• For example, suppose you create the following stored procedure:

41

CREATE PROCEDURE calc_payroll (payroll OUT NUMBER) AS CURSOR c1 IS SELECT sal, comm FROM emp;BEGIN payroll := 0; FOR c1rec IN c1 LOOP c1rec.comm := NVL(c1rec.comm, 0); payroll := payroll + c1rec.sal + c1rec.comm; END LOOP; /* Display debug info. */ DBMS_OUTPUT.PUT_LINE('Value of payroll: ' || TO_CHAR(payroll));END;

In SQL*Plus

SQL> SET SERVEROUTPUT ONSQL> VARIABLE num NUMBERSQL> CALL calc_payroll(:num);Value of payroll: 31225

42

Oracle Packages: UTL_FILE

• Package UTL_FILE allows your PL/SQL programs to read and write operating system (OS) text files.

• It provides a restricted version of standard OS stream file I/O, including open, put, get, and close operations.

43

UTL_FILE Functions• UTL_FILE.FOPEN ( location IN VARCHAR2, filename IN VARCHAR2, open_mode IN VARCHAR2) RETURN UTL_FILE.FILE_TYPE;

• Open_mode: 'r' , 'w‘, 'a‘• The maximum line size is the default to 1023.• To read a line of max. length > 1023, use • UTL_FILE.FOPEN ( location IN VARCHAR2, filename IN VARCHAR2, open_mode IN VARCHAR2, max_linesize IN BINARY_INTEGER) RETURN file_type;

44

UTL_FILE Functions

• UTL_FILE.IS_OPEN (file IN FILE_TYPE) RETURN BOOLEAN;• UTL_FILE.FCLOSE (file IN OUT FILE_TYPE);• UTL_FILE.GET_LINE ( file IN FILE_TYPE, buffer OUT VARCHAR2);

• Text is read up to but not including the line terminator, or up to the end of the file.

• If the line does not fit in the buffer, then a VALUE_ERROR exception is raised. If no text was read due to "end of file," then the NO_DATA_FOUND exception is raised.

• The maximum size of an input record is 1023 bytes.

45

BEGIN v_fid := utl_file.fopen('e:\log','h.log','r'); BEGIN

LOOP utl_file.get_line(v_fid,in_row);

IF substr(in_row,1,6)='Table' AND substr(in_row,-1,1) = ':' THEN h_table_name := rtrim(substr(in_row,7,30),':');

ELSEIF substr(in_row,-7,7) = 'loaded.' THEN h_no_rows := to_number(substr(in_row,3,instr (in_row,'R')-4)); ENDIF; END LOOP; EXCEPTION

WHEN NO_DATA_FOUND THEN NULL;utl_file.fclose(v_fid);

END;

46

Useful Links

• http://oraweb.comp.nus.edu.sg/RDBMS/appdev.816/a77069/toc.htm PL/SQL User's Guide and Reference

• http://www.elementkjournals.com/dbm/0005/dbm0053.htm Using the UTL_FILE package

47

Using SQL*Plus

• A client for users to interactively execute commands on Oracle Server.

• Useful commands– Describe a table structure: desc <table name>

– List all tables under you: select table_name from user_tables.

– Run packages: @<package name>

48

SQL*Plus Commands

• Show errors: show error;

• Edit the previously executed command(s):Edit

• Enable output on SQL*PLUS: SET SERVEROUTPUT ON

• Solve array overflow problem:SET ARRAYSIZE 1

49

SQL Commands• DROP TABLE employee• CREATE TABLE employee (

empno INTEGER NOT NULL,

name VARCHAR2(50) NOT NULL,

sal REAL NOT NULL,

primary key (empno));

• INSERT INTO employee VALUES (1, 'Jack', 6000)

• UPDATE employee SET sal=500 WHERE name=‘Jack’

• DELETE FROM employee WHERE name=‘Jack’;• CREATE INDEX test_index on employee(sal)• DROP INDEX test_index