MySQL CRUD基本操作

所谓 CRUD => Create , Read , Update , Delete 指的就是增删改查，为资料库一个很重要的地方。
前面我们做过C CREATE,R SELECT了，接下来要来操辍关于UPDATE、DELETE的部分。

UPDATE table_name set ...:UPDATE能够修改我们现有的资料。

透过,可以一次改变多个column。

UPDATE table_name set salary=8700,notes=updated where title="Software Engineer"+----+------------+-----------+-------------------+--------+------------+-------+| id | first_name | last_name | title             | salary | hire_date  | notes |+----+------------+-----------+-------------------+--------+------------+-------+|  1 | Robin      | Jackman   | Software Engineer |   8700 | 2001-10-12 | updated  ||  5 | Eliza      | Clifford  | Software Engineer |   8700 | 1998-10-19 | updated  ||  6 | Nancy      | Newman    | Software Engineer |   8700 | 2007-01-23 | updated  |+----+------------+-----------+-------------------+--------+------------+-------+

DELETE from table_name ...:删除特定资料。

DELETE from  employee  where title="Software Engineer";uery OK, 3 rows affected (0.01 sec)可发现其资料已经消失。mysql> SELECT * from employee;+----+------------+-----------+------------------------+--------+------------+-------+| id | first_name | last_name | title                  | salary | hire_date  | notes |+----+------------+-----------+------------------------+--------+------------+-------+|  2 | Taylor     | Edward    | Software Architect     |   7200 | 2002-09-21 | NULL  ||  3 | Vivian     | Dickens   | Database Administrator |   6000 | 2012-08-29 | NULL  ||  4 | Harry      | Clifford  | Database Administrator |   6800 | 2015-12-10 | NULL  ||  7 | Melinda    | Clifford  | Project Manager        |   8500 | 2013-10-29 | NULL  ||  8 | Jack       | Chan      | Test Engineer          |   6500 | 2018-09-07 | NULL  ||  9 | Harley     | Gilbert   | Software Architect     |   8000 | 2000-07-17 | NULL  |+----+------------+-----------+------------------------+--------+------------+-------+6 rows in set (0.00 sec)

DELETE from table_name 可以删除指定之table所有的资料。

CREATE TABLE IF NOT EXISTS table_name:IF NOT EXISTS代表如果这个table不存在，我们就执行CREATE TABLE，反之。

原本我们不加上IF NOT EXISTS虽然还是有执行INSERT的部分，但还是会报错，而加上以后，就没有报错INSERT的部分也有执行，整个代码会更加严谨。