case表达式详解

Posted 2020-10-07

CASE 表达式

---------格式一---------
CASE 条件表达式
  WHEN 条件表达式结果1 THEN 
     语句段1
  WHEN 条件表达式结果2 THEN
     语句段2
  ......
  WHEN 条件表达式结果n THEN
     语句段n
  [ELSE 条件表达式结果]
END;
---------格式二---------
CASE 
  WHEN 条件表达式1 THEN
     语句段1
  WHEN 条件表达式2 THEN
     语句段2
  ......
  WHEN 条件表达式n THEN 
     语句段n
  [ELSE 语句段]
END;

 

例4:

 1 DECLARE
 2   V_grade char(1) := UPPER(‘&p_grade‘);
 3   V_appraisal VARCHAR2(20);
 4 BEGIN
 5   V_appraisal :=
 6   CASE v_grade
 7     WHEN ‘A‘ THEN ‘Excellent‘
 8     WHEN ‘B‘ THEN ‘Very Good‘
 9     WHEN ‘C‘ THEN ‘Good‘
10     ELSE ‘No such grade‘
11   END;
12   DBMS_OUTPUT.PUT_LINE(‘Grade:‘||v_grade||‘  Appraisal: ‘|| v_appraisal);
13 END;

 

例5:

 

 1 DECLARE
 2    v_first_name employees.first_name%TYPE;
 3    v_job_id employees.job_id%TYPE;
 4    v_salary employees.salary%TYPE;
 5    v_sal_raise NUMBER(3,2);
 6 BEGIN
 7    SELECT first_name,   job_id,   salary INTO
 8           v_first_name, v_job_id, v_salary
 9    FROM employees WHERE employee_id = &emp_id;
10    CASE
11       WHEN v_job_id = ‘PU_CLERK‘ THEN
12          IF v_salary < 3000 THEN v_sal_raise := .08;
13          ELSE v_sal_raise := .07;
14          END IF;
15       WHEN v_job_id = ‘SH_CLERK‘ THEN
16          IF v_salary < 4000 THEN v_sal_raise := .06;
17          ELSE v_sal_raise := .05;
18          END IF;
19       WHEN v_job_id = ‘ST_CLERK‘ THEN
20          IF v_salary < 3500 THEN v_sal_raise := .04;
21          ELSE v_sal_raise := .03;
22          END IF;
23       ELSE
24          DBMS_OUTPUT.PUT_LINE(‘该岗位不涨工资: ‘||v_job_id);
25    END CASE;
26    DBMS_OUTPUT.PUT_LINE(v_first_name||‘的岗位是‘||v_job_id
27                                     ||‘、的工资是‘||v_salary
28                                     ||‘、工资涨幅是‘||v_sal_raise);
29 END;