> For the complete documentation index, see [llms.txt](https://chesterzhang666.gitbook.io/intro-mysql/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chesterzhang666.gitbook.io/intro-mysql/operation-to-table/modify-table.md).

# Modify Table

改变表的结构

## 增加表的列数

ALTER TABLE table\_name ADD 列1， 列2，...， 列N ;

```sql
#增加表的列数
ALTER TABLE t_student
ADD home_tel CHAR(11) NOT NULL;
```

## 改变表某一列的数据类型

```sql
#改变表某一列的数据类型
ALTER TABLE t_student MODIFY home_tel VARCHAR(20) NOT NULL;
```

## 改变表某一列的名称和约束

ALTER TABLE tablename CHANGE  parm newparm ;

```sql
#改变表某一列的名称和约束
ALTER TABLE student
CHANGE home_tel tel VARCHAR(20) ;

 
```

## 删除表的某一列

```sql
# 删除表的某一列
ALTER TABLE student
DROP tel;


```