mysql 常用命令整理

// 是否存在
mysql> use imss;
mysql> select  if(exists(select  *  from information_schema.columns where table_name = 'imss_righttemplate' and   column_name='id_righttemplate'),'yes','no') as cz ;

//主键

mysql> 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

mysql> alter table t2 add d timestamp;
mysql> alter table infos add ex tinyint not null default '0';
//删除列

mysql> alter table t2 drop column c;
//重命名列 

mysql> alter table t1 change a b integer;

//改变列的类型

mysql> alter table t1 change b b bigint not null;
mysql>alter table infos change list list tinyint not null default '0';

//重命名表

mysql> alter table t1 rename t2;
//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);
//加主关键字的索引

mysql> alter table tablename add primary key(id);
//加唯一限制条件的索引

mysql> alter table tablename add unique emp_name2(cardnumber);
//删除某个索引

mysql>alter table tablename drop index emp_name;

//增加字段

mysql> ALTER TABLE table_name ADD field_name field_type;
//修改原字段名称及类型

mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;
//删除字段

mysql> ALTER TABLE table_name DROP field_name;