可为NULL 但不能重复的SQL约束
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER trigger [dbo].[checkExamNo] on [dbo].[student]
for insert,update as
if exists(select examNo from student where isnull(examNo ,'')<>'' group by examNo having count(*)>1 )
rollback
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(低效)
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select batch_no "批次号",get_id "分类" from (
select(
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首先写一个js文件clearDatabaseBackup，内容如下
function deleteBackupFile(beforedays) {
var fso = new ActiveXObject ......
