PL/SQL嵌套IF-THEN-ELSE語句

在PL/SQL編程中嵌套IF-ELSE語句總是合法的，也就是說可以在一個IF或ELSE IF語句中使用另一個IF或ELSE IF語句。

語法

PL/SQL中嵌套IF-ELSE語句的語法是 -

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;

實例

請參考以下示例代碼 -

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;
/

當上述代碼在SQL提示符下執行時，它會產生以下結果 -