在PL/SQL编程中嵌套IF-ELSE语句总是合法的，也就是说可以在一个IF或ELSE IF语句中使用另一个IF或ELSE IF语句。

语法

PL/SQL中嵌套IF-ELSE语句的语法是 -

IF( boolean_expression 1)THEN 
   -- executes when the boolean expression 1 is true  
   IF(boolean_expression 2) THEN 
      -- executes when the boolean expression 2 is true  
      sequence-of-statements; 
   END IF; 
ELSE 
   -- executes when the boolean expression 1 is not true 
   else-statements; 
END IF;
SQL

实例

请参考以下示例代码 -

SET SERVEROUTPUT ON SIZE 1000000;
DECLARE 
   a number(3) := 100; 
   b number(3) := 200; 
BEGIN 
   -- check the boolean condition  
   IF( a = 100 ) THEN 
   -- if condition is true then check the following  
      IF( b = 200 ) THEN 
      -- if condition is true then print the following  
      dbms_output.put_line('Value of a is 100 and b is 200' ); 
      END IF; 
   END IF; 
   dbms_output.put_line('Exact value of a is : ' || a ); 
   dbms_output.put_line('Exact value of b is : ' || b ); 
END; 
/
SQL

当上述代码在SQL提示符下执行时，它会产生以下结果 -