sql 语句——功能实现【持续更新】

最近做项目用到一些数据操作，为了防止自己忘记，同时也供大家参考，特地将项目过程中写的sql语句发出来。

1.清空数据库中数据且不破坏表的结构(因为有表约束所以不能用：TRUNCATE TABLE 表名)

版本一：declare  cursor_alltablename cursor scroll dynamic for select name from sysobjects where xtype = 'U' and (not name like 'sys%') order by name desc;

declare @tablename varchar(50);
declare @strSql varchar(100);
open cursor_alltablename;
fetch next from cursor_alltablename into @tablename;
while (@@FETCH_STATUS = 0)
begin
 set @strSql='alter table ['+@tablename + '] nocheck constraint all'; --这里注意nocheck 和‘]’之间是有空格的，还有最好给@tablename加上'[]'
 exec (@strSql)
 fetch next from cursor_alltablename into @tablename
end

fetch first from cursor_alltablename into @tablename    --移到数据集的首部
while (@@FETCH_STATUS = 0)
begin
 set @strSql='delete ['+@tablename+']'
 print @strSql
 exec (@strSql)
 fetch next from cursor_alltablename into @tablename
end
fetch first from cursor_alltablename into @tablename
while (@@FETCH_STATUS = 0)
begin
 set @strSql='alter table ['+@tablename +'] check constraint all'
 exec (@strSql)
 fetch next from cursor_alltablename into @tablename
end
close cursor_alltablename
deallocate cursor_alltablename

改进版：

declare  cursor_alltablename cursor scroll dynamic for select name from sysobjects where xtype = 'U' and (not name like 'sys%') order by name desc;

declare @tablename nvarchar(50);
declare @strSql nvarchar(500);
declare @i int=1
open cursor_alltablename;
fetch next from cursor_alltablename into @tablename;
while (@@FETCH_STATUS = 0)
begin
 set @strSql=N'alter table ['+@tablename + N'] nocheck constraint all';
 exec (@strSql)
 set @i=@i+1
 fetch next from cursor_alltablename into @tablename
end

fetch last from cursor_alltablename into @tablename
while (@i > 0)
begin
 set @strSql=N'delete ['+@tablename+N']'
 print @strSql
 exec (@strSql)
 set @i = @i - 1
 fetch prior from cursor_alltablename into @tablename
end

declare @count int;
fetch first from cursor_alltablename into @tablename
while (@@FETCH_STATUS = 0)
begin
 set @strSql=N'alter table ['+@tablename +N'] check constraint all'
 exec (@strSql)
 --set @strSql = N'select @countOut=count(*) from sysobjects where parent_obj= OBJECT_ID(N'''+@tablename+N''') and xtype = N''PK'''; --这个是查询所有的主键列
 set @strSql = N'SELECT @countOut=count(*) FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME='''+@tablename+ --这个是查询自增列
  ''' AND (COLUMNPROPERTY(OBJECT_ID('''+@tablename+'''),COLUMN_NAME,''IsIdentity'')=1)'
 exec sp_executeSql @strSql,N'@countOut int Output',@countOut = @count Output;
 if(@count > 0) --将有主键自增的表的自增列置为0
  begin
   set @strSql = N'dbcc checkident(N'''+@tablename+N''',reseed,0)'
   exec (@strSql)
  end
 fetch next from cursor_alltablename into @tablename
end
close cursor_alltablename
deallocate cursor_alltablename

2.查询数据库中所有存在自增列的表

方法一：declare @Table_name varchar(60)

set @Table_name = '';

if Exists(Select top 1 1 from sysobjects
           Where objectproperty(id, 'TableHasIdentity') = 1
             and upper(name) = upper(@Table_name)
         )
     select 1
else select 0

-- or

if Exists(Select top 1 1 from sysobjects so
           Where so.xtype = 'U'
             and upper(so.name) = upper(@Table_name)
             and Exists(Select Top 1 1 from syscolumns sc
                         Where sc.id = so.id
                           and columnproperty(sc.id, sc.name, 'IsIdentity') = 1
                       )
         )
       select 1
else select 0

方法二：

SELECT COUNT(*) FROM INFORMATION_SCHEMA.columns WHERE TABLE_NAME='Orders'  AND (COLUMNPROPERTY(OBJECT_ID('Orders'),COLUMN_NAME,'IsIdentity')=1)

3.将数据库中表中自增列重新排列

exec sp_configure 'allow updates',1
reconfigure with override
GO

update syscolumns set colstat = 0 where id = object_id('dbo.Customer') and colstat = 1
GO

update   dbo.Customer 
set   ID=(select   count(1)   from   dbo.Customer   where   ID<=t.ID)   
from   dbo.Customer   t
GO

ueclare @a int 
set @a=(select count(*) from dbo.Customer)
DBCC CHECKIDENT (Customer, RESEED, @a)
GO

update syscolumns set colstat = 1 where id = object_id('dbo.Customer') and name = 'ID'
GO  
exec sp_configure 'allow updates',0
reconfigure with override