SQL中char、varchar 和nchar、nvarchar的区别,另外加一转换存储过程
。nchar、nvarchar的长度是在1到4000之间。和 char、varchar比较起来，nchar、nvarchar则最多存储4000个字符，不论是英文还是汉字；而char、varchar最多能存储 8000个英文，4000个汉字。可以看出使用nchar、nvarchar数据类型时不用担心输入的字符是英文还是汉字，较为方便，但在存储英文时数量上有些损失。 所以一般来说，如果含有中文字符，用nchar/nvarchar，如果纯英文和数字，用char/varchar。将所有的表中,数值类型由char,varchar改为nchar,nvarchar 的存储过程 /*--调用示例: exec p_set --*/ if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[p_set]') and OBJECTPROPERTY(id, N'IsProcedure') = 1) drop procedure [dbo].[p_set] GO create procedure p_set as declare tb cursor for Select sql='alter table ['+d.name +'] alter column ['+a.name+'] n' +b.name+'('+cast(a.length*2 as varchar)+')' FROM syscolumns a left join systypes b on a.xtype=b.xusertype inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties' where b.name in('char','varchar') and not exists(Select 1 FROM sysobjects where xtype='PK' and name in ( Select name FROM sysindexes Where indid in( Select indid FROM sysindexkeys Where id = a.id AND colid=a.colid ))) --主键不能修改 order by d.name,a.name declare @sql varchar(1000) open tb fetch next from tb into @sql while @@fetch_status = 0 begin exec(@sql) fetch next from tb into @sql end close tb deallocate tb go
