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

更多信息请查看IT技术专栏