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),
     description   VARCHAR(15)
);

向表中插入数据：

insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,Description)values(1,'Jason','Martin','19960725','20060725', 1234.56, 'Toronto','Programmer');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,Description)values(2,'Alison','Mathews','19760321','19860221', 6661.78, 'Vancouver','Tester');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,Description)values(3,'James','Smith','19781212', '19900315', 6544.78, 'Vancouver','Tester');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,Description)values(4,'Celia','Rice','19821024', '19990421', 2344.78, 'Vancouver','Manager');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,Description)values(5,'Robert','Black','19840115','19980808', 2334.78, 'Vancouver','Tester');
insert into Employee(id,first_name, last_name, start_date, end_Date, salary,City,Description)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,Description)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,Description)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      | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
|    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    |       |
| description | 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      | description |
+------+------------+------------+------------+---------+-----------+-------------+
|    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      |
+------+------------+------------+------------+---------+-----------+-------------+