工作中遇到的一道SQL应用题

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登录日志表

CREATE TABLE [dbo].[LoginLog]
(
[Seq] [int] NOT NULL IDENTITY(1, 1),  --Seq
[UserId] [varchar] (20) COLLATE Chinese_PRC_CI_AS NULL, --用户名
[LoginTime] [datetime] NULL, --登录时间
[SuccessFlg] [bit] NULL, --登录是否成功

) ON [PRIMARY]
GO

需求：返回用户是否能继续登录

登录规则：如果用户1小时内登录三次错误，则锁定1天内无法登录

实现SQL

SELECT CASE WHEN COUNT(1) = 3 THEN 1 ELSE 0 END LockFlg
FROM (
SELECT TOP 3 l.* FROM LoginLog l with(nolock)
INNER JOIN (
		SELECT TOP 1 Seq,SuccessFlg,LoginTime,UserId FROM dbo.LoginLog with(nolock)
		WHERE UserId=‘sdf333‘ AND LoginTime >= DATEADD(DAY,-1,GETDATE())
		ORDER BY Seq DESC
) lastLog ON l.Seq  <= lastLog.Seq AND l.UserId = lastLog.UserId
WHERE  DATEDIFF(HOUR, l.LoginTime,lastLog.LoginTime) < 1
ORDER BY l.Seq  desc
) AS t
WHERE t.successflg = 0

公司的一位新人对SQL挺有兴趣的。就让他试试。给到的SQL：

SELECT  COUNT(1) LockFlg FROM 
(
SELECT 
CASE WHEN COUNT(*)=3 THEN 1 ELSE 0 END AS near3,
CASE WHEN DATEDIFF(HOUR,MIN(t.LoginTime),MAX(t.LoginTime))<1 THEN 1 ELSE 0 END AS inonehour,
CASE WHEN SUM(CAST(t.SuccessFlg AS INT) )=0 THEN 1 ELSE 0 END AS wrongtimes,
CASE WHEN DATEDIFF(HOUR,MAX(t.LoginTime),GETDATE())<24 THEN 1 ELSE 0 END AS inoneday
FROM 
(
SELECT TOP 3 * FROM dbo.LoginLog
WHERE UserId=‘sdf333‘
ORDER BY logintime DESC 
)t
)tt
WHERE near3=1 AND inonehour=1 AND wrongtimes=1 AND inoneday=1

这位同学的思路更简单直接，感觉我已经老了~~~

工作中遇到的一道SQL应用题

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原文地址：http://www.cnblogs.com/miku/p/4292249.html