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
[code]
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
[code]
ELSIF THEN

ELSIF THEN

ELSEEND 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;
/