Oracle PL/SQL Nutshell

Oracle PL/SQL Nutshell

持續更新中。。。

Basic Syntax & Variables

Basic Structure

PL/SQL can be executed from SQL Plus

• Called PL/SQL blocks
• Anonymous blocks as they do not have a name
• Procedures/functions are named blocks

[Declare]
BEGIN
[Exception]
END

Examples

VAR P_SET VARCHAR2(20)
BEGIN
    :P_SET := 'Hello world'; -- colon(:)variable_name, bind variable
END;

SET SERVEROUTPUT ON
BEGIN
    dbms_output.put_line('Hello world');
END;

Oracle Architecture

Variables

• Used throughout PL/SQL
• Holding area for data
• Default values, constants
• Values from the database
• Populated with :=

VAR_NAME [CONSTANT] datatype [NOT NULL] [:= value]

Name conventions

prefix	meaning
V_	standard variable
C_	constant
P_	variable that will be used/originated in SQL Plus
G_	variable used within multiple PL/SQL blocks

With prefix you can use preserved words

• Declare variables in DECLARE section
• := or SELECT INTO
• Use all the SQL data types
• Can use syntax %TYPE and %ROWTYPE to establish variables with database properties - type inheritance/runtime inheritance

Data types

Scalar types

Number

• BINARY_DOUBLE
• BINARY_FLOAT
• BINARY_INTEGER
• DEC
• DECIMAL
• DOUBLE PRECISION
• FLOAT
• INT
• INTEGER
• NATURAL
• NATURALN
• NUMBER
• NUMERIC
• PLS_INTEGER
• POSITIVE
• POSITIVEN
• REAL
• JSONTYPE
• SMALLINT

Characters

• CHAR
• CHARACTER
• LONG
• LONG RAW
• NVARCHAR2
• RAW
• ROWO
• STRING
• UROWO
• VARCHAR
• VARCHAR2

Boolean

• BOOLEAN

Date

• DATE
• DATETIME

Composite types

• RECORD
• TABLE
• VARRAY

Reference types

• REF CURSOR
• REF object_type

LOB types

• BFILE
• BLOB
• CLOB
• NCLOB

Variable scope

• Can nest PL/SQL blocks - blocks within blocks
• Inner blocks can see outer blocks variables
• Outer blocks cannot see inner block variables

DECLARE
V_V1 NUMBER;
BEGIN
V_V1 := 1;
    DECLARE
    V_V2 NUMBER;
    BEGIN
    V_V1 := V_V2;
    END;
DBMS_OUTPUT...
END;

Create type

DECLARE
TYPE emp_info IS RECORD (
    v_ename emp.ename%TYPE,
    v_sal emp.sal%TYPE
);
emp_rec emp_info;
emp_rec2 emp%ROWTYPE;

Control Flow

Logic Flow

IF…ELSIF…ELSE

IF <condition> THEN
    <statements>;
ELSIF <condition> THEN
    <statements>;
ELSE
    <statements>;
END IF;

CASE WHEN

CASE
    WHEN <condition> THEN
        <statements>;
    WHEN <condition> THEN
        <statements>;
    ELSE
        <statements>
END;

LOOP

LOOP

LOOP
    <statements>;
    EXIT LOOP WHEN <condition>;
END LOOP;

WHILE

WHILE <condition> THEN
    <statements>;
END;

FOR LOOP

FOR <var_> IN var_
LOOP
    <statements>;
END LOOP;

CURSOR

DECLARE
    CURSOR c1 IS
        SELECT prod_id,cust_id, time_id, amount_sold
        FROM sales
        WHERE amount_sold > 100;
    c1_rec c1%ROWTYPE;
    l_cust_firstname customers.cust_firstname%TYPE;
    l_cust_lastname customers.cust_lastname%TYPE;
BEGIN
    FOR c1_rec IN c1
    LOOP
        ...
    END LOOP;
END;