MySQL 基本語法 (十二) Subquery

Subquery 子查詢

(在一個查詢語句裡面塞入另一個查詢語句)

1. 找出研發部門的經理名字

(1)用一個查詢取找`branch`中研發部門經理的`manager_id`

SELECT `manager_id` FROM `branch`
WHERE `branch_name` = '研發';

(2)再寫另一個查詢，這個查詢利用剛剛的查詢結果(`manager_id`)去找`employee`中員工id是206的名字

SELECT `name`
FROM `employee`
WHERE `emp_id` = (
	SELECT `manager_id` FROM `branch`
	WHERE `branch_name` = '研發'
);

等同於這個意思 :

SELECT `name`
FROM `employee`
WHERE `emp_id` = 206;

2. 找出對單一位客戶銷售金額超過50000的員工名字

 SELECT `employee`.`name` FROM `employee`
 WHERE `employee`.`emp_id` IN (
		SELECT `works_with`.`emp_id` FROM `works_with`
		WHERE `total_sales` > 50000
 );