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(
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
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MySQL-关系代数-并、交、差、等值连接、自然连接、左连接。。。
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