数据库出现了问题，能详细说明一下吗？。

出错提示：
未更新任何行
未提交行xx中的数据 //xx代表行号
错误源:Microsoft.VisualStudio.DataTools
错误信息:自从上次检索数据后,更新的行已被更改或删除

请更正错误并重试,或按Esc取消更改。

错误信息:自从上次检索数据后,更新的行已被更改或删除

看看这个论坛的数据库结构吧，比较经典： if exists (select * from sysobjects where id = object_id(n'[dbo]. [announce]') and objectproperty(id, n'isusertable') = 1) drop table [dbo].[announce] go if exists (select * from sysobjects where id = object_id(n'[dbo]. [board]') and objectproperty(id, n'isusertable') = 1) drop table [dbo].[board] go if exists (select * from sysobjects where id = object_id(n'[dbo]. [essence]') and objectproperty(id, n'isusertable') = 1) drop table [dbo].[essence] go if exists (select * from sysobjects where id = object_id(n'[dbo]. [site]') and objectproperty(id, n'isusertable') = 1) drop table [dbo].[site] go if exists (select * from sysobjects where id = object_id(n'[dbo]. [user]') and objectproperty(id, n'isusertable') = 1) drop table [dbo].[user] go create table [dbo].[announce] ( [announceid] [int] identity (1, 1) not null , [parentid] [int] null , [child] [int] null , [boardid] [int] null , [username] [nvarchar] (50) null , [useremail] [nvarchar] (255) null , [url] [nvarchar] (255) null , [urltitle] [nvarchar] (255) null , [urlpic] [nvarchar] (255) null , [topic] [nvarchar] (255) null , [body] [ntext] null , [dateandtime] [nvarchar] (50) null , [hits] [int] null , [length] [int] null , [rootid] [int] null , [layer] [int] null , [orders] [int] null , [emote] [int] null , [ip] [nvarchar] (20) null , [signature] [nvarchar] (255) null ) on [primary] textimage_on [primary] go create table [dbo].[board] ( [boardid] [int] identity (1, 1) not null , [boardname] [nvarchar] (100) null , [boardmaster] [int] null , [ignoreip] [nvarchar] (255) null ) on [primary] go create table [dbo].[essence] ( [id] [int] identity (1, 1) not null , [announceid] [int] null , [boardid] [int] null , [username] [nvarchar] (50) null , [useremail] [nvarchar] (255) null , [url] [nvarchar] (255) null , [urltitle] [nvarchar] (255) null , [urlpic] [nvarchar] (255) null , [topic] [nvarchar] (255) null , [body] [ntext] null , [dateandtime] [nvarchar] (50) null , [hits] [int] null , [length] [int] null , [emote] [int] null ) on [primary] textimage_on [primary] go create table [dbo].[site] ( [sitemasterpwd] [nvarchar] (50) null ) on [primary] go insert into [site]([sitemasterpwd]) values("intels") go create table [dbo].[user] ( [userid] [int] identity (1, 1) not null , [username] [nvarchar] (50) null , [useremail] [nvarchar] (255) null , [userpassword] [nvarchar] (11) null , [icq] [nvarchar] (20) null , [homepage] [nvarchar] (255) null , [sex] [nvarchar] (10) null , [passanswer] [nvarchar] (100) null , [lastvisit] [smalldatetime] null , [incometime] [smalldatetime] null , [birthday] [smalldatetime] null , [points] [int] null , [visits] [int] null , [country] [nvarchar] (20) null , [city] [nvarchar] (20) null , [passquest] [nvarchar] (100) null , [signature] [nvarchar] (255) null ) on [primary] go alter table [dbo].[announce] with nocheck add constraint [pk_announce] primary key nonclustered ( [announceid] ) on [primary] go alter table [dbo].[board] with nocheck add constraint [pk_board] primary key nonclustered ( [boardid] ) on [primary] go alter table [dbo].[essence] with nocheck add constraint [pk_essence] primary key nonclustered ( [id] ) on [primary] go alter table [dbo].[user] with nocheck add constraint [pk_user] primary key nonclustered ( [userid] ) on [primary] go create index [announce_i] on [dbo].[announce]([rootid], [parentid]) on [primary] go create index [boardid] on [dbo].[announce]([boardid]) on [primary] go create index [boardid] on [dbo].[essence]([boardid]) on [primary] go create index [points] on [dbo].[user]([points]) on [primary] go create index [username] on [dbo].[user]([username]) on [primary] go