请问如何将数据库中所有表中的text类型转成varchar500？

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CREATE PROC p_ToUnicode

@type tinyint=0  --修改方式，0=仅查询可修改情况,1=仅所有列可修改时才修改,2=修改可修改列，报告不可修改列

AS

SET NOCOUNT ON

--查询非unicode列转换为unicode列的可行性

SELECT TableName=o.name,FieldName=c.name,

FieldType=t.name N'(' CAST(c.prec as varchar) N')'

CASE WHEN c.isnullable=1 THEN N'' ELSE N' NOT' END

N' NULL',

NoChangeCause=CAST(STUFF(

CASE WHEN COLUMNPROPERTY(c.id,c.name,N'IsComputed')=1

THEN N',计算列' ELSE N'' END

CASE WHEN c.cdefault=0 THEN N'' ELSE N',列具有默认值' END

CASE WHEN EXISTS(

SELECT * FROM sysindexkeys idxk,sysindexes idx

WHERE idxk.id=c.id

AND idxk.colid=c.colid

AND idxk.id=idx.id

AND idxk.indid=idx.indid

AND idx.indid NOT IN(0,255)

AND INDEXPROPERTY(idx.id,idx.name,N'IsAutoStatistics')=0)

THEN N',列被主键、唯一键、索引、STATISTICS引用' ELSE N'' END

CASE WHEN EXISTS(

SELECT * FROM sysforeignkeys WHERE fkeyid=c.id AND fkey=c.colid)

THEN N',列被外键约束引用' ELSE N'' END

CASE WHEN EXISTS(

SELECT * FROM sysobjects oc,sysdepends d

WHERE oc.parent_obj=o.id

AND OBJECTPROPERTY(oc.id,N'IsCheckCnst')=1

AND d.id=oc.id

AND d.depnumber=c.colid)

THEN N',列被CHECK约束引用' ELSE N'' END,1,1,N'') as nvarchar(4000))

INTO # FROM sysobjects o,syscolumns c,systypes t

WHERE o.id=c.id and o.status>=0

AND OBJECTPROPERTY(o.id,N'IsUserTable')=1

AND t.xusertype=c.xusertype

AND t.name in('char','varchar')

IF @@ROWCOUNT=0 RETURN

--假如需要，修改非unicode列为unicode列

IF @type=2 OR NOT EXISTS(SELECT * FROM # WHERE NoChangeCause>'')

BEGIN

SET XACT_ABORT ON

BEGIN TRAN

DECLARE tb CURSOR LOCAL

FOR

SELECT N'ALTER TABLE ' QUOTENAME(TableName)

N' ALTER COLUMN ' QUOTENAME(FieldName)

N' N' FieldType

FROM #

WHERE NoChangeCause IS NULL

DECLARE @sql nvarchar(4000)

OPEN tb

FETCH tb INTO @sql

WHILE @@FETCH_STATUS=0

BEGIN

EXEC sp_executesql @sql

FETCH tb INTO @sql

END

CLOSE tb

DEALLOCATE tb

COMMIT TRAN

END

--显示不能修改的列

SELECT TableName,FieldName,FieldType,

NoChangeCause=ISNULL(NoChangeCause,N'可以修改(或者已经修改成功)')

FROM #

ORDER BY CASE WHEN NoChangeCause IS NULL THEN 1 ELSE 0 END,TableName