ALTER TABLE
改变表

The ALTER TABLE statement is used to add or drop columns in an existing table.
ALTER TABLE语句可以用来给现有的表进行添加或是删除栏目的操作。

ALTER TABLE table_name 

ADD column_name datatype

ALTER TABLE table_name 
DROP COLUMN column_name

Note: Some database systems don't allow the dropping of a column in a database table (DROP COLUMN column_name).
注意：一些数据库系统不允许删除表中的栏目（DROP COLUMN 栏目名）

Person表:

Example
举例

To add a column named "City" in the "Person" table:
给这张"Person"表加一个名为"City"的栏目：

ALTER TABLE Person ADD City varchar(30)

Result:
结果：

Example
举例

To drop the "Address" column in the "Person" table:
删除"Person"表中的"Address"栏目

ALTER TABLE Person DROP COLUMN Address

Result:
结果：

SQL Create View

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