Mysql主键相关的sql语句集锦

添加表字段

alter table table1 add transactor varchar(10) not Null;

alter table   table1 add id int unsigned not Null auto_increment primary key

修改某个表的字段类型及指定为空或非空

alter table 表名称 change 字段名称 字段名称 字段类型 [是否允许非空];

alter table 表名称 modify 字段名称 字段类型 [是否允许非空];

alter table 表名称 modify 字段名称 字段类型 [是否允许非空];

修改某个表的字段名称及指定为空或非空

alter table 表名称 change 字段原名称 字段新名称 字段类型 [是否允许非空

删除某一字段

ALTER TABLE mytable DROP 字段 名;

添加唯一键

ALTER TABLE `test2` ADD UNIQUE ( `userid`)

修改主键

ALTER TABLE `test2` DROP PRIMARY KEY ,ADD PRIMARY KEY ( `id` )

增加索引

ALTER TABLE `test2` ADD INDEX ( `id` )

ALTER TABLE `category ` MODIFY COLUMN `id`  int(11) NOT NULL AUTO_INCREMENT FIRST ,ADD PRIMARY KEY (`id`);

修改主键的sql语句块如下:

22 declare @defname varchar(100)
declare @cmd varchar(500)
declare @tablename varchar(100)
declare @keyname varchar(100)
Set @tablename=Temp1
Set @keyname=id --需要設置的key,分隔
select @defname= name
   FROM sysobjects so
   JOIN sysconstraints sc
   ON so.id = sc.constid
   WHERE object_name(so.parent_obj) = @tablename
   and xtype=PK
if @defname is not null
begin
select @cmd=alter table + @tablename+ drop constraint + @defname
--print @cmd
   exec (@cmd)
 end
else
 set @defname=PK_+@keyname
select @cmd=alter table + @tablename+ ADD constraint + @defname + PRIMARY KEY CLUSTERED(+@keyname+)
   exec (@cmd)

　　如何取主键字段名称及字段类型--得到主键字段名

1:
SELECT TABLE_NAME,COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE

WHERE TABLE_NAME<>dtproperties

2:
EXEC sp_pkeys @table_name=表名

3:
select o.name as 表名,c.name as 字段名,k.colid as 字段序号,k.keyno as 索引顺序,t.name as 类型

from sysindexes i

join sysindexkeys k on i.id = k.id and i.indid = k.indid

join sysobjects o on i.id = o.id

join syscolumns c on i.id=c.id and k.colid = c.colid

join systypes t on c.xusertype=t.xusertype

where o.xtype = U and o.name=要查询的表名

and exists(select 1 from sysobjects where xtype = PK and parent_obj=i.id and name = i.name)

order by o.name,k.colid