update 表名
set text类型字段名=replace(convert(varchar(8000),text类型字段名),'要替换的字符','替换成的值')
1.update ntext:
(1)varchar和nvarchar类型是支持replace，所以如果你的text/ntext不超过8000/4000可以先转换成前面两种类型再使用replace。
|
update 表名
set text类型字段名=replace(convert(varchar(8000),text类型字段名),'要替换的字符','替换成的值')
|
|
update 表名
set ntext类型字段名=replace(convert(nvarchar(4000),ntext类型字段名),'要替换的字符','替换成的值')
|
(2)如果text/ntext超过8000/4000,看如下例子
|
declare @pos int
declare @len int
declare @str nvarchar(4000)
declare @des nvarchar(4000)
declare @count int
set @des ='<requested_amount+1>'--要替换成的值
set @len=len(@des)
set @str= '<requested_amount>'--要替换的字符
set @count=0--统计次数.
WHILE 1=1
BEGIN
select @pos=patINDEX('%'+@des+'%',字段名) - 1
from 表名
where 条件
IF @pos>=0
begin
DECLARE @ptrval binary(16)
SELECT @ptrval = TEXTPTR(字段名)
from 表名
where 条件
UPDATETEXT 表名.字段名 @ptrval @pos @len @str
set @count=@count+1
end
ELSE
break;
END
select @count
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
declare @pos int
declare @len int
declare @str nvarchar(4000)
declare @des nvarchar(4000)
declare @count int
set @des ='<replace>'--要替换成的值
set @len=len(@des)
set @str= '<replace>'--要替换的字符
set @count=0--统计次数.
DECLARE tnames_cursor CURSOR
FOR
SELECT pkid
FROM ob_userskin
OPEN tnames_cursor
--DECLARE @tablename ntext(16)
declare @id int
FETCH NEXT FROM tnames_cursor INTO @id
WHILE (@@FETCH_STATUS = 0)
BEGIN
WHILE 1=1
BEGIN
select @pos=patINDEX('%'+@des+'%',main) - 1
from ob_userskin
where pkid=@id
IF @pos>=0
begin
DECLARE @ptrval binary(16)
SELECT @ptrval = TEXTPTR(main)
from ob_userskin where pkid=@id
UPDATETEXT ob_userskin.main @ptrval @pos @len @str
set @count=@count+1
end
ELSE
break;
END
FETCH NEXT FROM tnames_cursor INTO @id
END
CLOSE tnames_cursor
DEALLOCATE tnames_cursor
select @count
|
2.alter column语句有局限性,比如不允许修改text、image、ntext 或 timestamp 列.
以下提供一个修改ntext列的例子:
|
Alter Table tbl Add newcol ntext null
go
update tbl set newcol=col
go
EXEC sp_rename 'tbl.col', 'oldcol', 'COLUMN'
go
EXEC sp_rename 'tbl.newcol', 'col', 'COLUMN'
go
alter table tbl drop column oldcol
go
|
以上通过新增一列替换旧的列方法实现了将一个不允许为空的ntext修改为允许为空的ntext列(注意:以上的go不能缺少).修改表结构之后,由于视图所依赖的基础对象的更改，视图的持久元数据会过期,需要刷新视图,通过sp_refreshview (可以通过sp_depends 找处相关的视图,再通过sp_refreshview逐个刷新).
另外可以也可以通过一下存储过程进行刷新所有视图:
|
PRINT 'Refreshing all views...'
DECLARE @vName sysname
DECLARE refresh_cursor CURSOR FOR
SELECT Name from sysobjects WHERE xtype = 'V'
order by crdate
FOR READ ONLY
OPEN refresh_cursor
FETCH NEXT FROM refresh_cursor
INTO @vName
WHILE @@FETCH_STATUS <> -1
BEGIN
exec sp_refreshview @vName
PRINT '视图' + @vName + ' refreshed'
FETCH NEXT FROM refresh_cursor
INTO @vName
END
CLOSE refresh_cursor
DEALLOCATE refresh_cursor
|
