懒人懒到家 批量修改DB中字段类型

---------这里举例 varchar  转 nvarchar 类型

---------将DB中 字段为varchar(10)的改为nvarchar(20)
---------字段为varchar(20)的改为nvarchar(40)

declare @tb_name Nvarchar(120)
declare @column_name Nvarchar(120)
declare @max_len int
declare @sql nvarchar(max)

declare cur_cur cursor for
select b.name, a.name as column_name ,a.max_length from sys.all_columns a join sys.sysobjects b on a.object_id=b.id and b.xtype='U'
join sys.types c on a.user_type_id=c.user_type_id and c.name ='varchar' and c.user_type_id =167 and (a.max_length =10 or a.max_length =20)
open cur_cur
fetch next from cur_cur into @tb_name,@column_name,@max_len
while @@FETCH_STATUS =0
begin
if @max_len =10
begin
set @sql=N'alter table '+@tb_name+' alter column'+@column_name+' nvarchar(20)'
end
if @max_len=20
begin
set @sql=N'alter table '+@tb_name+' alter column'+@column_name+' nvarchar(40)'
end
EXEC SP_EXECUTESQL @SQL
fetch next from cur_cur into @tb_name,@column_name,@max_len
end
close cur_cur
deallocate cur_cur