mysql使用命令行删除表中的字段

mysql使用命令行删除表中的字段，基本语法如下：

alter table <表名> drop column <字段名>;

创建一个表：

CREATE TABLE Employee(
     id            int,
     first_name    VARCHAR(15),
     last_name     VARCHAR(15),
     start_date    DATE,
     end_date      DATE,
     salary        FLOAT(8,2),
     city          VARCHAR(10),
     de ion   VARCHAR(15)
);

向表中插入数据：

insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(1,\'Jason\',\'Martin\',\'19960725\',\'20060725\', 1234.56, \'Toronto\',\'Programmer\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(2,\'Alison\',\'Mathews\',\'19760321\',\'19860221\', 6661.78, \'Vancouver\',\'Tester\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(3,\'James\',\'Smith\',\'19781212\', \'19900315\', 6544.78, \'Vancouver\',\'Tester\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(4,\'Celia\',\'Rice\',\'19821024\', \'19990421\', 2344.78, \'Vancouver\',\'Manager\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(5,\'Robert\',\'Black\',\'19840115\',\'19980808\', 2334.78, \'Vancouver\',\'Tester\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(6,\'Linda\', \'Green\', \'19870730\', \'19960104\', 4322.78,\'New York\',\'Tester\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(7,\'David\',\'Larry\',\'19901231\', \'19980212\', 7897.78,\'New York\',\'Manager\');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,De ion)values(8,\'James\',\'Cat\', \'19960917\',\'20020415\', 1232.78,\'Vancouver\', \'Tester\');

查看表数据：

mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id   | first_name | last_name | start_date | end_date   | salary  | city      | de ion |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | Martin    | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | Mathews   | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | Smith     | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | Rice      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | Black     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | Green     | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | Larry     | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | Cat       | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+-----------+------------+------------+---------+-----------+-------------+

删除表中Last_Name字段：

ALTER TABLE employee DROP Last_Name;

使用desc命令查看表详细：

mysql> desc employee;
+-------------+-------------+------+-----+---------+-------+
| Field       | Type        | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| id          | int(11)     | YES  |     | NULL    |       |
| first_name  | varchar(15) | YES  |     | NULL    |       |
| start_date  | date        | YES  |     | NULL    |       |
| end_date    | date        | YES  |     | NULL    |       |
| salary      | float(8,2)  | YES  |     | NULL    |       |
| city        | varchar(10) | YES  |     | NULL    |       |
| de ion | varchar(15) | YES  |     | NULL    |       |
+-------------+-------------+------+-----+---------+-------+

再使用select语句查看表数据，我们可以发现Last_Name字段已经不在表里面了。

mysql> select * from Employee;
+------+------------+------------+------------+---------+-----------+-------------+
| id   | first_name | start_date | end_date   | salary  | city      | de ion |
+------+------------+------------+------------+---------+-----------+-------------+
|    1 | Jason      | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto   | Programmer  |
|    2 | Alison     | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester      |
|    3 | James      | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester      |
|    4 | Celia      | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager     |
|    5 | Robert     | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester      |
|    6 | Linda      | 1987-07-30 | 1996-01-04 | 4322.78 | New York  | Tester      |
|    7 | David      | 1990-12-31 | 1998-02-12 | 7897.78 | New York  | Manager     |
|    8 | James      | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester      |
+------+------------+------------+------------+---------+-----------+-------------+