oracle case when 語句的用法詳解
阿新 • • 發佈:2020-11-16
CASE WHEN 表示式有兩種形式
--簡單Case函式
CASE sex
WHEN '1' THEN '男'
WHEN '2' THEN '女'
ELSE '其他' END
--Case搜尋函式
CASE
WHEN sex = '1' THEN '男'
WHEN sex = '2' THEN '女'
ELSE '其他' END
CASE WHEN 在語句中不同位置的用法
SELECT CASE WHEN 用法
SELECT grade, COUNT (CASE WHEN sex = 1 THEN 1 /*sex 1為男生,2位女生*/ ELSE NULL END) 男生數, COUNT (CASE WHEN sex = 2 THEN 1 ELSE NULL END) 女生數 FROM students GROUP BY grade;
WHERE CASE WHEN 用法
SELECT T2.*, T1.* FROM T1, T2 WHERE (CASE WHEN T2.COMPARE_TYPE = 'A' AND T1.SOME_TYPE LIKE 'NOTHING%' THEN 1 WHEN T2.COMPARE_TYPE != 'A' AND T1.SOME_TYPE NOT LIKE 'NOTHING%' THEN 1 ELSE 0 END) = 1
GROUP BY CASE WHEN 用法
SELECT CASE WHEN salary <= 500 THEN '1' WHEN salary > 500 AND salary <= 600 THEN '2' WHEN salary > 600 AND salary <= 800 THEN '3' WHEN salary > 800 AND salary <= 1000 THEN '4' ELSE NULL END salary_class, -- 別名命名 COUNT(*) FROM Table_A GROUP BY CASE WHEN salary <= 500 THEN '1' WHEN salary > 500 AND salary <= 600 THEN '2' WHEN salary > 600 AND salary <= 800 THEN '3' WHEN salary > 800 AND salary <= 1000 THEN '4' ELSE NULL END;