关于PLSQL的CASE语句有什么问题？

Question

我正在编写一个简单的CASE来在员工获得更多的部门AVG工资时在屏幕上打印。但是我不明白为什么我在屏幕上看到只有一个结果，当我想检查2名员工的工资时。我希望你能理解我的问题。谢谢。

SET SERVEROUTPUT ON 

DECLARE 
    v_emp121_sal employees.salary%TYPE; 
    v_emp121_lname employees.last_name%TYPE; 

    v_emp139_sal employees.salary%TYPE; 
    v_emp139_lname employees.last_name%TYPE; 

    v_avgsal  employees.salary%TYPE; 
BEGIN 
    SELECT salary, last_name 
    INTO v_emp121_sal, v_emp121_lname 
    FROM employees 
    WHERE employee_id = 121; 
    DBMS_OUTPUT.PUT_LINE('EMPLOYEE 121 SALARY IS: ' || v_emp121_sal); 

    SELECT salary, last_name 
    INTO v_emp139_sal, v_emp139_lname 
    FROM employees 
    WHERE employee_id = 139; 
    DBMS_OUTPUT.PUT_LINE('EMPLOYEE 139 SALARY IS: ' || v_emp139_sal); 

    SELECT AVG(salary) 
    INTO v_avgsal 
    FROM employees 
    WHERE department_id = 50; 
    DBMS_OUTPUT.PUT_LINE('DEPARTMENT 50 AVG SALARY IS: ' || 
          TRUNC(v_avgsal, 0)); 


    CASE 
     WHEN 
      v_emp121_sal < v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp121_lname || 
           ' IS LESS THAN DEPARTMENT AVG'); 
     WHEN 
      v_emp121_sal > v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp121_lname || 
           ' IS HIGHER THAN AVG DEPARTMENT'); 
     WHEN 
      v_emp139_sal < v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp139_lname || 
           ' IS LESS THAN DEPARTMENT AVG'); 
     WHEN 
      v_emp139_sal > v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp139_lname || 
           ' IS HIGHER THAN AVG DEPARTMENT'); 
    END CASE; 

END; 
/

理论，我应该接受在屏幕上 “EMP抚顺石油化工研究院的工资比AVG DEPARTMENT较高的” “EMP SEO的工资比AVG DEPARTMENT LESS”

Answer 1

一个case表达返回一个值。如果两名员工需要单独输出，请使用2 case表达式，以便每个表达式都返回自己的值。

CASE 
     WHEN 
      v_emp121_sal < v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp121_lname || 
           ' IS LESS THAN DEPARTMENT AVG'); 
     WHEN 
      v_emp121_sal > v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp121_lname || 
           ' IS HIGHER THAN AVG DEPARTMENT'); 
END CASE; 

CASE 
     WHEN 
      v_emp139_sal < v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp139_lname || 
           ' IS LESS THAN DEPARTMENT AVG'); 

     WHEN 
      v_emp139_sal > v_avgsal THEN 
      DBMS_OUTPUT.PUT_LINE('SALARY OF EMP ' || v_emp139_lname || 
           ' IS HIGHER THAN AVG DEPARTMENT'); 
END CASE; 

你可能要添加一个条件=以及这样就可以避免一个null输出时>或<条件失败。