更新表
增加或删减列、创建或取消索引、更改原有列的数据类型、重新命名列或表、更改表的评注
和表的引擎类型
Alter (ignore) table *** +…
Add column:alter table mysql_test.customers
Add column cust_city char(10) not null default ‘Wuhan’ after cust_sex;
First/after
类似:add primary key(首先删除表中已有的主键)、add foreign key、add index
Change column:alter table mysql_test.customers
Change cust_sex sex char(1) null default ‘M’;
Alter column:修改或删除表中指定列的默认值
Alter table mysql_test.customers
Alter column cust_city set default ‘Beijing’;
Modify column:只会修改制定列的数据类型,而不会干涉它的列名
Alter table mysql_test.customers
Modify column cust_name char(20) first;
First/after
Drop column:类似:drop primary key、drop foteign key、drop index
Rename to:alter table mysql_test.customers
Rename to mysql_test.backup_customers;