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

修改某個表的字段類型及指定為空或非空

alter table 表名稱 change 字段名稱 字段名稱 字段類型 [是否允許非空];

alter table 表名稱 modify 字段名稱 字段類型 [是否允許非空];

alter table 表名稱 modify 字段名稱 字段類型 [是否允許非空];

修改某個表的字段名稱及指定為空或非空

alter table 表名稱 change 字段原名稱 字段新名稱 字段類型 [是否允許非空

刪除某一字段

ALTER TABLE mytable DROP 字段 名;

添加唯一鍵

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

修改主鍵

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`);

修改主鍵的sql語句塊如下:

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)

　　如何取主鍵字段名稱及字段類型--得到主鍵字段名

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 字段序號,k.keyno as 索引順序,t.name as 類型

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='要查詢的表名'

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

order by o.name,k.colid

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