我在 PL SQL 中的 CASE 语句有什么问题？

Question

我正在编写一个简单的 CASE 代码，以便在员工赚取更多部门的 AVG 工资时打印在屏幕上。但是我不明白为什么当我想检查 2 名员工的工资时，我在屏幕上只看到一个结果。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;
/

理论上，我应该在屏幕上收到 “EMP FRIPP 的薪水高于平均部门” "EMP SEO 的薪水低于平均部门"

Answer 1

case 表达式返回一个值。如果您需要为两名员工提供单独的输出，请使用 2 个case 表达式，以便每个人都返回自己的值。

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;

您可能还想为= 添加一个条件，以便在> 或< 条件失败时避免null 输出。