oracle if 语句的使用

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: <'||v||'>'); end; /