MSsql中default的用法

[习惯性蹭分]

alter table tablename alter column columnname set default 'value'

在网上看的关于default约束，但是会报“关键字 'set' 附近有语法错误。”的错误出来。
大家帮忙看下。

[快溜]

alter table tablename alter column columnname default 'value'

[dovei]

#1正确

alter table tablename alter column columnname default 'value'

[中国风]

Create table tablename(columnname nvarchar(50))
go
alter table tablename add constraint UQ_tablenam_columnname default 'value' for columnname;

[习惯性蹭分]

[Quote=引用 2 楼 dovei 的回复:]

#1正确
SQL code
alter table tablename alter column columnname default 'value'
[/Quote]
关键字 'default' 附近有语法错误。

[习惯性蹭分]

[Quote=引用 3 楼 roy_88 的回复:]

SQL code
Create table tablename(columnname nvarchar(50))
go
alter table tablename add constraint UQ_tablenam_columnname default 'value' for columnname;
[/Quote]
我用的是MSsql2008,正解哦。TKS

[pengxuan]

if object_id('tb','U') is not null
   drop table tb
go
create table tb
(
 id int identity(1,1),
 name varchar(10)
)
go
alter table tb add constraint tb_name_def default 'abc' for name

[pengxuan]

[ CONSTRAINT constraint_name ]
{
{ PRIMARY KEY | UNIQUE }
[ CLUSTERED | NONCLUSTERED ]
(column [ ASC | DESC ] [ ,...n ] )
[ WITH FILLFACTOR =fillfactor
[ WITH ( <index_option>[ , ...n ] ) ]
[ ON { partition_scheme_name (partition_column_name ... )
| filegroup | "default" } ]
| FOREIGN KEY
(column [ ,...n ] )
REFERENCES referenced_table_name [ ( ref_column [ ,...n ] ) ]
[ ON DELETE { NO ACTION | CASCADE | SET NULL | SET DEFAULT } ]
[ ON UPDATE { NO ACTION | CASCADE | SET NULL | SET DEFAULT } ]
[ NOT FOR REPLICATION ]
| DEFAULT constant_expression FOR column [ WITH VALUES ]
| CHECK [ NOT FOR REPLICATION ] (logical_expression )
}

[黄_瓜]

alter table tb add constraint XXOO default 'xx' for oo
--就是加了一个约束，默认值也是一种约束

[黄_瓜]

如果改变的话需要先删除了

alter table tb drop  XXOO

alter table tb add constraint XXOO default 'xoxo' for oo