JumpStart PL/SQL
Wang Hao
1
Outline
• PL/SQL Programming
• SQL*Plus and SQL commands
2
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.
3
Benefits of PL/SQL
• Integration of applications, shared library
and Oracle server.
• Improve performance.
application
application
SQL
IF … THEN
SQL
ELSE
SQL
END IF;
Other DBMSs
Oracle with
PL/SQL
4
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
5
PL/SQL Block Structure(1)
DECLARE
v_variable VARCHAR2(5);
BEGIN
SELECT column_name
INTO
v_variable
FROM table_name
EXCEPTION …
WHEN exception_name THEN
END;
6
Block Types
[DECLARE]
Function
Procedure
PROCEDURE name IS
FUNCTION name
RETURN datatype IS
BEGIN
BEGIN
BEGIN
-- statements
-- statements
[EXCETPION]
[EXCETPION]
-- statements
RETURN value;
[EXCETPION]
END;
END;
END;
7
Program Constructs
• Anonymous Block
– Unnamed PL/SQL block that is embedded within an
application or is issued interactively
• Stored procedure or function
Named PL/SQL block stored in Oracle Server that can
accept parameters and be invoked repeatedly by name.
• Package
Named PL/SQL module that groups related procedures,
functions and identifiers. Stored in Oracle server or
Oracle Developer components – for example, Forms.
8
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.
9
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.
10
Declaring PL/SQL Variables
• Examples:
Declare
v_hiredate
v_deptno
v_location
v_tax_rate
c_comm
DATE
NUMBER(2) NOT NULL :=10;
VARCHAR(13) := ‘New York’;
NUMBER(3,2) := 3.0;
CONSTANT NUMBER := 1400;
• Guidelines:
– Follow naming conventions.
– Initialize variables designated as NOT NULL.
– Declare at most one identifier per line.
11
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.
12
Declaring Variables with the %
TYPE attribute
• Declare a variable according to
– A database column definition
– Another previously declared variables.
• Prefix % TYPE
• Examples:
v_ename
v_balance
v_min_balance
emp.ename%TYPE;
NUMBER(7,2);
v_balance%TYPE := 10;
13
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 */
14
Operators
• Arithmetic
+ , -, *, / , **,
• Comparison
=, <, >, >=, <=, !=, IS NULL, LIKE, BETWEEN, IN
• Assignment
:=
• Statement terminator
;
• String concatenation
||
• Logical
NOTG, AND , OR
15
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)
16
SELECT Statements in PL/SQL
• Retrieve data from the database with SELECT.
• Example:
DECLARE
v_dept_no NUMBER(2);
v_loc
VARCHAR2(15);
BEGIN
SELECT
deptno, loc
INTO
v_deptno, v_loc
FROM
dept
WHERE
dname=‘SALES’;
END;
17
Manipulating Data Using PL/SQL
• INSERT
BEGIN
INSERT INTO emp(empno, ename, job, deptno)
VALUES (empno_sequence.NEXTVAL, ‘Jack’,
‘CTO’, 10);
END;
• UPDATE
BEGIN
UPDATE emp
SET
sal = sal + 10;
WHERE job = ‘ANALYST’;
END;
18
Manipulating Data Using PL/SQL
• DELETE
BEGIN
DELETE FROM emp
WHERE name = ‘JACK’;
END;
19
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;
20
Writing Control Structures
• Iterative control: loop statements
– Basic loop
– FOR loop
– WHIE loop
• Basic loop
BEGIN
LOOP
INSERT INTO item(ordid, itemid)
VALUES (610, v_counter);
v_counter := counter + 1;
EXIT WHEN v_counter > 10;
END LOOP;
COMMIT;
END;
21
Writing Control Structures
• FOR loop
BEGIN
FOR i IN 1..100 LOOP
……
END LOOP;
END;
• WHILE loop
BEGIN
WHILE i <= 100 LOOP
……
END LOOP;
END;
• Nested loop is allowed.
22
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.
23
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.
24
Writing Explicit Cursors
• Use explicit cursors to individually process each
row returned by a multi-row SELECT statement.
Cursor
7369
7430
Active Set
SMITH
CLERK
JONES
MANAGER
7788
SCOTT
ANALYST
7789
JACK
CTO
Current Row
25
Writing Explicit Cursors: Example
DECLARE
v_empno
emp.empno%TYPE;
v_ename
emp.ename%TYPE;
CURSOR emp_cursor IS
SELECT empno, ename
FROM emp;
BEGIN
OPEN emp_cursor;
LOOP
FETCH emp_cursor INTO v_empno, v_ename;
EXIT WHEN emp_cursor%NOTFOUND;
……
END LOOP;
CLOSE emp_cursor;
26
Cursors with Parameters
• Example: pass the department number and job title
to the WHERE clause.
DECALRE
CURSOR emp_cursor
(p_deptno NUMBER, p_job VARCHAR2) IS
SELECT
empno, ename
FROM
emp
WHERE
deptno = v_deptno
AND
job = v_job;
BEGIN
OPEN emp_cursor(10, ‘CLERK’);
……
27
Cursors with Subqueries
DECALRE
CURSOR my_cursor IS
SELECT t1.deptno, t1.dname, t2.STAFF
FROM
dept t1, (SELECT deptno,
count(*) STAFF
FROM
emp
GROUP BY deptno) t2
WHERE t1.deptno = t2.deptno
AND
t2.STAFF >= 5;
28
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;
BEGIN
FOR i IN 1..25
v1(i) := 1;
END LOOP;
END;
29
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:
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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
...
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END debit_account;
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;
32
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.
33
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.
34
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:
35
• 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:
36
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;
37
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.
38
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', ...);
39
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:
40
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 ON
SQL> VARIABLE num NUMBER
SQL> CALL calc_payroll(:num);
Value of payroll: 31225
41
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.
42
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;
43
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.
44
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;
45
Useful Links
• http://oraweb.comp.nus.edu.sg/RDBMS/app
dev.816/a77069/toc.htm PL/SQL User's
Guide and Reference
• http://www.elementkjournals.com/dbm/000
5/dbm0053.htm Using the UTL_FILE
package
46
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>
47
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
48
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)
49
• DROP INDEX test_index