mysql基础话语 - IDC云服务

mysql基础语句

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++mysql 基础操作

//主键549830479

   alter table tabelname add new_field_id int(5) unsigned default 0 not null auto_increment ,add primary key (new_field_id);

//增加一个新列549830479

   alter table t2 add d timestamp;

alter table infos add ex tinyint not null default ‘0’;

//删除列549830479

   alter table t2 drop column c;

//重命名列549830479

   alter table t1 change a b integer;

//改变列的类型549830479

   alter table t1 change b b bigint not null;

alter table infos change list list tinyint not null default ‘0’;

//重命名表549830479

   alter table t1 rename t2;

加索引549830479

   mysql> alter table tablename change depno depno int(5) not null;

mysql> alter table tablename add index 索引名 (字段名1[，字段名2 …]);

mysql> alter table tablename add index emp_name (name);

加主关键字的索引549830479

mysql> alter table tablename add primary key(id);

加唯一限制条件的索引549830479

mysql> alter table tablename add unique emp_name2(cardnumber);

删除某个索引549830479

   mysql>alter table tablename drop index emp_name;

修改表：549830479

增加字段：549830479

   mysql> ALTER TABLE table_name ADD field_name field_type;

修改原字段名称及类型：549830479

   mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

删除字段：549830479

   mysql> ALTER TABLE table_name DROP field_name;

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++mysql 约束

——–添加主键约束(bookid作为主键)

alter table bookmessage

add constraint pk_bookid primary key(bookid)

——–添加唯一约束

alter table bookmessage

add constraint uq_bookid UNIQUE(bookid)

———添加默认约束

alter table bookmessage

add constraint df_address DEFAUIT(‘地址不详’) for Address

——–添加检出约束,要求年龄只能在15—40之间

alter table readermessage

add constraint CK_age CHECK(age BETWEEN 15 AND 40)

——-添加外键约束

alter table bookmessage

add constraint fk_bookid

foreign key(bookid)<外键> references readermessage<表>(readerid)<表中的主键>

——-删除约束

alter table 表名

drop constraint 约束名

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

相关文章：

你感兴趣的文章：

标签云：