MySQL 基本語法 (四) UPDATE & DELETE

UPDATE & DELETE : 修改刪除資料

UPDATE 修改資料

SET SQL_SAFE_UPDATES=0;

原來的student TABLE

• 把major中的'英語'改成'英語文學'

UPDATE `student`
SET `major` = '英語文學'
WHERE `major` = '英語';

SELECT * FROM `student`;

• 把student_id=3的major改成'生物'

UPDATE `student`
SET `major` = '生物'
WHERE `student_id` = '3';

SELECT * FROM `student`;

• 把'生物'和'化學'改成'生化'

UPDATE `student`
SET `major` = '生化'
WHERE `major` = '生物' OR `major` = '化學';

SELECT * FROM `student`

• 改變多個屬性

UPDATE `student`
SET `name` = '小灰', `major` = '生化'
WHERE `student_id` = 1;

SELECT * FROM `student`

• 沒有設定WHERE，預設成更改全部的值

UPDATE `student`
SET `major` = '物理';

SELECT * FROM `student`​

DELETE 刪除資料

• 刪除student_id=4的資料

DELETE FROM `student`
WHERE `student_id` = 4;

SELECT * FROM `student`;

• 刪除符合2個指定條件的資料

DELETE FROM `student`
WHERE `name` = '小灰' AND `major` = '物理';

SELECT * FROM `student`;

• 根據成績刪除資料

> 大於 < 小於 >= 大於等於 <=小於等於 =等於 <>不等於

DELETE FROM `student`
WHERE `score` < 60;

SELECT * FROM `student`;

• 刪除表格中所有的資料

DELETE FROM `student` ;

SELECT * FROM `student`;​