PL/SQL - 嵌套的 IF-THEN-ELSE 语句

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  简述

  在 PL/SQL 编程中嵌套 IF-ELSE 语句，这意味着您可以使用一个 IF 要么 ELSE IF 在另一个内部声明 IF 要么 ELSE IF 声明。
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  句法

  
  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; 
  

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  例子

  
  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; 
  / 
  

  在 SQL 提示符下执行上述代码时，会产生以下结果 -

  
  Value of a is 100 and b is 200 
  Exact value of a is : 100 
  Exact value of b is : 200  
  PL/SQL procedure successfully completed.