IF语句的使用

A.基本的IF条件语句：

基本语法:

程序代码

IF THEN

END IF;

Example:

程序代码

SQL> set serveroutput on;

SQL> declare

x number(3):=9;

begin

if x<10 then

dbms_output.put_line('x is less than10');

end if;

end;

/

结果：

x is less than10

PL/SQL procedure successfully completed

B.IF - ELSE 语句

基本语法：

程序代码

IF THEN

ELSE

END IF;

Example:

程序代码

DECLARE

x NUMBER(3) := 10;

BEGIN

IF x < 10 THEN

dbms_output.put_line('X is less than 10');

ELSE

dbms_output.put_line('X is not less than 10');

END IF;

END;

/

结果：

X is not less than 10

PL/SQL procedure successfully completed

C:IF - ELSIF - ELSE 语句

基本语法:

程序代码

IF THEN

ELSIF THEN

ELSIF THEN

ELSE

END IF;

Example:

程序代码

set serveroutput on

DECLARE

x NUMBER(3) := 47;

BEGIN

IF x < 10 THEN

dbms_output.put_line('X is less than 10');

ELSIF x = 10 THEN

dbms_output.put_line('X is equal to 10');

ELSIF x < 100 THEN

dbms_output.put_line('X is between 11 and 99');

ELSE

dbms_output.put_line('X is greater than 99');

END IF;

END;

/

结果：

X is between 11 and 99

PL/SQL procedure successfully completed

D:与NULL值比较处理

Example:

程序代码

declare

v NUMBER;

begin

if v = 1 then

DBMS_OUTPUT.put_line('Equal to 1');

elsif v!= 1 then

DBMS_OUTPUT.put_line('Not equal to 1');

elsif v = v then

DBMS_OUTPUT.put_line('Equal to itself');

else

DBMS_OUTPUT.put_line('Undefined result');

end if;

v:=v+1;

DBMS_OUTPUT.put_line('New value: ');

end;

/