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MySQL常用SQL语句

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

2.增加一个新列
alter table t2 add d timestamp;
alter table infos add ex tinyint not null default ’0′;

3.删除列
alter table t2 drop column c;

4.重命名列
alter table t1 change a b integer;

5.改变列的类型
alter table t1 change b b bigint not null;
alter table infos change list list tinyint not null default ’0′;

6.重命名表
alter table t1 rename t2;

7.加索引
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);

8.加主关键字的索引
mysql> alter table tablename add primary key(id);

9.加唯一限制条件的索引
mysql> alter table tablename add unique emp_name2(cardnumber);

10.删除某个索引
mysql>alter table tablename drop index emp_name;

11.增加字段:
mysql> ALTER TABLE table_name ADD field_name field_type;

12.修改原字段名称及类型:
mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

13.删除字段:
mysql> ALTER TABLE table_name DROP field_name;

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