起风网已经有快2个月没有更新博客了，实在是因为最近发生了太多的事情，辞了工作，在湘雅医院待了一个多月，然后又新换了工作……
在平时的工作中，Sqlserver中许多知识点是经常用到的，但是有时候我们往往忽略了它们，在过去的一年里，一直使用的是Mysql，现在又开始接触Sqlserver了，所以就把一些常用又容易忽视的Sqlserver知识点总结一点，以便备忘之用。
所有的操作都将基于Northwind数据库来进行操作。
注意：当采用附加Northwind数据库的方式进行数据库迁移的时候，可能会出现错误：“Access is denied”。解决方案： right-click the SQL Server Management Studio icon and select Run as administrator。
数据在线Mock地址：https://www.mockaroo.com/
SET NOCOUNT ON 介绍
在存储过程中，经常用到SET NOCOUNT ON；
作用：阻止在结果集中返回显示受T-SQL语句或则usp影响的行计数信息。
当SET NOCOUNT ON 时候，不返回计数，当SET NOCOUNT OFF时候，返回计数。
当SET NOCOUNT ON 时候，会更新@@RowCount，但是不向客户端发送存储过程每个语句的DONE_IN_proc消息。
如果存储过程中包含一些并不返回实际数据的语句，使用SET NOCOUNT ON时，网络通信流量便会大量减少，可以显著提高应用程序性能。
SET NOCOUNT 指定的设置只在执行或运行时候生效，分析时候不生效。
示例：
USE NorthwindGOSET NOCOUNT OFF;SELECT TOP 5 OrderDate FROM OrdersGO
执行结果如下：
USE NorthwindGOSET NOCOUNT ON;SELECT TOP 5 OrderDate FROM OrdersGO
执行结果如下：
Go 介绍
如果只是执行一条语句，有没有GO都一样。
如果多条语句之间用GO分隔开就不一样了。
每个被GO分隔的语句都是一个单独的事务，一个语句执行失败不会影响其它语句执行。
GO 不是 Transact-SQL 语句；而是可为 SQL Server 查询分析器识别的命令。
如果你的SQL过长的时候，就要写GO，或者有一些语句，它只能是第一句操作的，在之前你也得写 GO ，GO的意思是分批处理语句，有加这个 GO ，就执行GO 行的代码，执行后再执行接下来的代码。
像以下这种情况下就要用到GO ，以达到分批处理数据的目的，否则将会报错。
IF EXISTS(SELECT 1 FROM sys.views WHERE name='View_OrderInfo')DROP VIEW View_OrderInfocreate view View_OrderInfoasselect c.ContactName,c.CompanyName,o.OrderDate,o.ShipName,o.OrderID,o.Freight from [Orders] o inner join Customers c on o.CustomerID=c.CustomerID
会报错
必须是：
IF EXISTS(SELECT 1 FROM sys.views WHERE name='View_OrderInfo')DROP VIEW View_OrderInfoGOcreate view View_OrderInfoasselect c.ContactName,c.CompanyName,o.OrderDate,o.ShipName,o.OrderID,o.Freight from [Orders] o inner join Customers c on o.CustomerID=c.CustomerID
select count(*) count(1) count(2) count(‘a’) 之间的区别
count(*)：找表中最短的列进行统计行数
count(1) count(2) count(‘a’)：对常数列进行统计行数。它们的执行方式是一样的，没有任何区别。
很显然采用count(1) count(2) count(‘a’)的方式，效率会更高，因为count(*)会先去算出最短的列，然后再去统计。虽然现在的Sqlserver查询分析器自动会帮我们做一些优化，但是我们必须知道它们的实现原理。
WITH (NOLOCK)
缺点:
1.会产生脏读
2.只适用于select查询语句
优点:
1.有些文章说，加了WITH (NOLOCK)的SQL查询效率可以增加33%。
2.可以用于inner join 或者left join等语句
脏读: 一个用户对一个资源做了修改，此时另外一个用户正好读取了这条被修改的记录，然后，第一个用户放弃修改，数据回到修改之前，这两个不同的结果就是脏读。
详细内容:
要提升SQL的查询效能，一般来说大家首先会考虑建立索引(index)。其实除了index的建立之外，当我们在下SQL Command时，在语法中加一段WITH (NOLOCK)可以改善在线大量查询的环境中数据集被LOCK的现象藉此改善查询的效能。
不过有一点千万要注意的就是，WITH (NOLOCK)的SQL SELECT有可能会造成Dirty Read(脏读)。
例如：
SELECT o.OrderID,o.OrderDate,o.Freight,d.Quantity,d.UnitPriceFROM [dbo].[Orders] o WITH (NOLOCK)JOIN [dbo].[Order Details] d WITH (NOLOCK)ON o.OrderID=d.OrderID
DELETE、INSERT、UPDATE这些需要transaction的指令就不能使用WITH (NOLOCK)。
加了WITH (NOLOCK)即告诉SQL Server，我们的这段SELECT指令无需去考虑目前table的transaction lock状态，因此效能上会有明显的提升，而且数据库系统的Lock现象会有明显的减少(包含Dead Lock)。
当使用NoLock时，它允许阅读那些已经修改但是还没有交易完成的数据。因此如果有需要考虑transaction事务数据的实时完整性时，使用WITH (NOLOCK)就要好好考虑一下。
如果不需考虑transaction，WITH (NOLOCK)或许是个好用的参考。
Sqlserver高效分页
在SQLserver2012之前，分页我们一般是使用ROW_NUMBER()。以获取第11条到第50条数据为例：
ROW_NUMBER()的实现方式：
select * from ( select *, ROW_NUMBER() OVER(Order by a.OrderID DESC ) AS RowNumber from Orders as a ) as b where RowNumber BETWEEN 11 and 50
SQLserver2012中OFFSET & FETCH实现方式：
SELECT o.* FROM dbo.Orders oORDER BY o.OrderID DESC OFFSET 10 ROWS FETCH NEXT 40 ROWS ONLY
OFFSET & FETCH实现方式 更加精简更加高效。
使用 OFFSET-FETCH 中的限制
- ORDER BY 是使用 OFFSET 和 FETCH 子句所必需的。
- OFFSET 子句必须与 FETCH 一起使用。永远不能使用 ORDER BY … FETCH。
- TOP 不能在同一个查询表达式中与 OFFSET 和 FETCH 一起使用。
- OFFSET/FETCH 行计数表达式可以是将返回整数值的任何算术、常量或参数表达式。该行计数表达式不支持标量子查询
ALTER PROCEDURE getLightningSendOverTimeOrder --闪电送到期存储过程(@OverTimeMinutes INT,--超时时间阈值@GetLasterDay int --取最近多少天的订单)AsDECLARE @sql NVARCHAR(MAX);BEGINset nocount on;set @Sql=N'WITH OrderInfo --查询近一天的，处理超时的闪电送订单 AS ( SELECT ID , CommunityId , SubOrderNumber FROM dbo.[Order] WITH ( NOLOCK ) WHERE DATEDIFF(day, CreatedOn, GETDATE()) <= @GetLasterDay AND DATEDIFF(mi, CreatedOn, ModifiedOn) > @OverTimeMinutes AND LightningSend = 1 AND IsDeleted = 0 --待付款(商品订单),待确认(商品订单),待发货(商品订单),待收货(商品订单) AND OrderStatusId IN ( ''C2EE784F-F29B-4E18-8D73-761264339005'', ''FA1A31DF-3855-41BB-9F5C-A09F3AB4C408'', ''ACF190B2-0CA2-43A0-8E6B-70DF8521F4C5'', ''15F06407-C82C-4CA8-984E-37FB3BD9963C'' ) ), SmsOrder --没有发送过信息的订单 AS ( SELECT o.ID , o.CommunityId , o.SubOrderNumber FROM OrderInfo o WITH ( NOLOCK ) where not EXISTS(SELECT 1 FROM [dbo].[Sms_LightningSendOrderOverTime] lso WITH ( NOLOCK ) WHERE o.SubOrderNumber = lso.SubOrderNumber) ), SmsOrderInfo AS ( SELECT so.CommunityId , so.SubOrderNumber , p.PublisherId , c.ConvenienceStoreID , oi.ProductId , p.CategoryId , p.ProcessType FROM SmsOrder AS so WITH ( NOLOCK ) INNER JOIN Community c WITH ( NOLOCK ) ON so.CommunityId = c.ID INNER JOIN dbo.OrderItem oi WITH ( NOLOCK ) ON so.ID = oi.OrderId INNER JOIN dbo.Product p WITH ( NOLOCK ) ON oi.ProductId = p.Id AND p.LightningSend = 1 AND p.ProcessType != 1 -- 便利店 ), MerchantSmsOrderInfo AS ( SELECT so.CommunityId , so.SubOrderNumber , p.PublisherId , c.ConvenienceStoreID , oi.ProductId , p.CategoryId , p.ProcessType FROM SmsOrder AS so WITH ( NOLOCK ) INNER JOIN Community c WITH ( NOLOCK ) ON so.CommunityId = c.ID INNER JOIN dbo.OrderItem oi WITH ( NOLOCK ) ON so.ID = oi.OrderId INNER JOIN dbo.Product p WITH ( NOLOCK ) ON oi.ProductId = p.Id AND p.LightningSend = 1 AND p.ProcessType = 1 -- 商家 ), ResultInfo AS ( SELECT usr.Id AS UserId , soi.SubOrderNumber , usr.PhoneNumber FROM SmsOrderInfo AS soi INNER JOIN dbo.[User] AS usr WITH ( NOLOCK ) ON soi.ConvenienceStoreID = usr.OrgId INNER JOIN dbo.Organization org WITH ( NOLOCK ) ON usr.OrgId = org.Id AND org.Levels = 2 --便利店 INNER JOIN OrderDistributaryCategoryRelation AS odcr WITH ( NOLOCK ) ON usr.Id = odcr.MerchantUserId AND odcr.CategoryType = 1 AND odcr.SellerId = soi.ConvenienceStoreID AND odcr.CategoryId = soi.CategoryId INNER JOIN OrderDistributary AS odb WITH ( NOLOCK ) ON usr.Id = odb.MerchantUserId AND odb.SellerId = soi.ConvenienceStoreID INNER JOIN OrderDistributaryRelation AS odbr WITH ( NOLOCK ) ON usr.Id = odbr.MerchantUserId AND odbr.MerchantId = soi.ConvenienceStoreID UNION ALL SELECT u.Id AS UserId , soi.SubOrderNumber , u.PhoneNumber FROM dbo.[User] u WITH ( NOLOCK ) INNER JOIN OrderDistributary odb WITH ( NOLOCK ) ON u.Id = odb.MerchantUserId AND odb.IsDefault = 1 INNER JOIN SmsOrderInfo soi WITH ( NOLOCK ) ON odb.SellerId = soi.ConvenienceStoreID ------------------------------商家----------------------------- UNION ALL SELECT usr.Id AS UserId , soi.SubOrderNumber , usr.PhoneNumber FROM MerchantSmsOrderInfo AS soi INNER JOIN dbo.[User] AS usr WITH ( NOLOCK ) ON soi.ConvenienceStoreID = usr.OrgId INNER JOIN dbo.Organization org WITH ( NOLOCK ) ON usr.OrgId = org.Id AND org.Levels = 1 --商家 INNER JOIN OrderDistributaryCategoryRelation AS odcr WITH ( NOLOCK ) ON usr.Id = odcr.MerchantUserId AND odcr.CategoryType = 1 AND odcr.CategoryId = soi.CategoryId INNER JOIN OrderDistributary AS odb WITH ( NOLOCK ) ON usr.Id = odb.MerchantUserId AND odb.SellerId = soi.PublisherId INNER JOIN OrderDistributaryRelation AS odbr WITH ( NOLOCK ) ON odcr.MerchantUserId = odbr.MerchantUserId AND odbr.MerchantId = soi.ConvenienceStoreID UNION ALL SELECT u.Id AS UserId , soi.SubOrderNumber , u.PhoneNumber FROM MerchantSmsOrderInfo soi WITH ( NOLOCK ) INNER JOIN OrderDistributary odb WITH ( NOLOCK ) ON odb.SellerId = soi.PublisherId AND odb.IsDefault = 1 AND odb.IsDeleted = 0 INNER JOIN dbo.[User] u WITH ( NOLOCK ) ON u.Id = odb.MerchantUserId ) SELECT r.SubOrderNumber , r.UserId, r.PhoneNumber FROM ResultInfo r 'exec sp_executesql @Sql,N'@OverTimeMinutes int,@GetLasterDay int',@OverTimeMinutes,@GetLasterDay;SET NOCOUNT OFF;END
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自己写的一个存储过程例子
--------------------------------------创建闪电送存储过程-----------------------------------IF EXISTS(Select Name From Sysobjects Where Name='getLightningSendOverTimeOrder' And Xtype='P')DROP PROCEDURE [dbo].getLightningSendOverTimeOrderGOCREATE PROCEDURE getLightningSendOverTimeOrder --闪电送到期存储过程(@OverTimeMinutes INT,--超时时间阈值@GetLasterDay int --取最近多少天的订单)AsDECLARE @sql NVARCHAR(MAX);BEGINset nocount on;set @Sql=N'WITH OrderInfo --查询近一天的，处理超时的闪电送订单 AS ( SELECT ID , CommunityId , SubOrderNumber FROM dbo.[Order] WITH ( NOLOCK ) WHERE DATEDIFF(day, CreatedOn, GETDATE()) <= @GetLasterDay AND DATEDIFF(mi, CreatedOn, ModifiedOn) > @OverTimeMinutes AND LightningSend = 1 AND IsDeleted = 0 --待付款(商品订单),待确认(商品订单),待发货(商品订单),待收货(商品订单) AND OrderStatusId IN ( ''C2EE784F-F29B-4E18-8D73-761264339005'', ''FA1A31DF-3855-41BB-9F5C-A09F3AB4C408'', ''ACF190B2-0CA2-43A0-8E6B-70DF8521F4C5'', ''15F06407-C82C-4CA8-984E-37FB3BD9963C'' ) UNION ALL--状态一直是待支付状态的SELECT ID , CommunityId , SubOrderNumber FROM dbo.[Order] WITH ( NOLOCK ) WHERE DATEDIFF(day, CreatedOn, GETDATE()) <=@GetLasterDay AND LightningSend = 1 AND IsDeleted = 0 AND (OrderStatusId =''ACF190B2-0CA2-43A0-8E6B-70DF8521F4C5'' AND DATEDIFF(mi, CreatedOn, GETDATE()) >@OverTimeMinutes) ), SmsOrder --需要发送过信息的订单 AS ( SELECT o.ID , o.CommunityId , o.SubOrderNumber FROM OrderInfo o WITH ( NOLOCK ) where not EXISTS(SELECT 1 FROM [dbo].[Sms_LightningSendOrderOverTime] lso WITH ( NOLOCK ) WHERE o.SubOrderNumber = lso.SubOrderNumber) ), SmsOrderInfo AS ( SELECT so.CommunityId , so.SubOrderNumber , p.PublisherId , c.ConvenienceStoreID , oi.ProductId , p.CategoryId , p.ProcessType FROM SmsOrder AS so WITH ( NOLOCK ) INNER JOIN Community c WITH ( NOLOCK ) ON so.CommunityId = c.ID INNER JOIN dbo.OrderItem oi WITH ( NOLOCK ) ON so.ID = oi.OrderId INNER JOIN dbo.Product p WITH ( NOLOCK ) ON oi.ProductId = p.Id AND p.LightningSend = 1 AND p.ProcessType != 1 -- 便利店 ), MerchantSmsOrderInfo AS ( SELECT so.CommunityId , so.SubOrderNumber , p.PublisherId , c.ConvenienceStoreID , oi.ProductId , p.CategoryId , p.ProcessType FROM SmsOrder AS so WITH ( NOLOCK ) INNER JOIN Community c WITH ( NOLOCK ) ON so.CommunityId = c.ID INNER JOIN dbo.OrderItem oi WITH ( NOLOCK ) ON so.ID = oi.OrderId INNER JOIN dbo.Product p WITH ( NOLOCK ) ON oi.ProductId = p.Id AND p.LightningSend = 1 AND p.ProcessType = 1 -- 商家 ), ResultInfo AS ( SELECT usr.Id AS UserId , soi.SubOrderNumber , usr.PhoneNumber FROM SmsOrderInfo AS soi INNER JOIN dbo.[User] AS usr WITH ( NOLOCK ) ON soi.ConvenienceStoreID = usr.OrgId INNER JOIN dbo.Organization org WITH ( NOLOCK ) ON usr.OrgId = org.Id AND org.Levels = 2 --便利店 INNER JOIN OrderDistributaryCategoryRelation AS odcr WITH ( NOLOCK ) ON usr.Id = odcr.MerchantUserId AND odcr.CategoryType = 1 AND odcr.SellerId = soi.ConvenienceStoreID AND odcr.CategoryId = soi.CategoryId INNER JOIN OrderDistributary AS odb WITH ( NOLOCK ) ON usr.Id = odb.MerchantUserId AND odb.SellerId = soi.ConvenienceStoreID INNER JOIN OrderDistributaryRelation AS odbr WITH ( NOLOCK ) ON usr.Id = odbr.MerchantUserId AND odbr.MerchantId = soi.ConvenienceStoreID UNION ALL SELECT u.Id AS UserId , soi.SubOrderNumber , u.PhoneNumber FROM dbo.[User] u WITH ( NOLOCK ) INNER JOIN OrderDistributary odb WITH ( NOLOCK ) ON u.Id = odb.MerchantUserId AND odb.IsDefault = 1 INNER JOIN SmsOrderInfo soi WITH ( NOLOCK ) ON odb.SellerId = soi.ConvenienceStoreID ------------------------------商家----------------------------- UNION ALL SELECT usr.Id AS UserId , soi.SubOrderNumber , usr.PhoneNumber FROM MerchantSmsOrderInfo AS soi INNER JOIN dbo.[User] AS usr WITH ( NOLOCK ) ON soi.ConvenienceStoreID = usr.OrgId INNER JOIN dbo.Organization org WITH ( NOLOCK ) ON usr.OrgId = org.Id AND org.Levels = 1 --商家 INNER JOIN OrderDistributaryCategoryRelation AS odcr WITH ( NOLOCK ) ON usr.Id = odcr.MerchantUserId AND odcr.CategoryType = 1 AND odcr.CategoryId = soi.CategoryId INNER JOIN OrderDistributary AS odb WITH ( NOLOCK ) ON usr.Id = odb.MerchantUserId AND odb.SellerId = soi.PublisherId INNER JOIN OrderDistributaryRelation AS odbr WITH ( NOLOCK ) ON odcr.MerchantUserId = odbr.MerchantUserId AND odbr.MerchantId = soi.ConvenienceStoreID UNION ALL SELECT u.Id AS UserId , soi.SubOrderNumber , u.PhoneNumber FROM MerchantSmsOrderInfo soi WITH ( NOLOCK ) INNER JOIN OrderDistributary odb WITH ( NOLOCK ) ON odb.SellerId = soi.PublisherId AND odb.IsDefault = 1 AND odb.IsDeleted = 0 INNER JOIN dbo.[User] u WITH ( NOLOCK ) ON u.Id = odb.MerchantUserId ) SELECT r.SubOrderNumber , r.UserId, r.PhoneNumber FROM ResultInfo r 'exec sp_executesql @Sql,N'@OverTimeMinutes int,@GetLasterDay int',@OverTimeMinutes,@GetLasterDay;SET NOCOUNT OFF;ENDGO
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demo2:分页存储过程
------------------------------------------创建我的优惠券存储过程 created by zouqj-2017-3-1-----------------------------------IF EXISTS(Select Name From Sysobjects Where Name='usp_GetMyCouponsList' And Xtype='P')DROP PROCEDURE usp_GetMyCouponsListGOCREATE PROC usp_GetMyCouponsList(@PageIndex int, --页码@PageSize int, --@hostName nvarchar(100),--服务器地址@MemberID UNIQUEIDENTIFIER, --会员ID@IsGetTotalInfo BIT, --是否得到统计信息，1为得到统计信息，0为不得到统计信息，返回记录集@HasStatus BIT, -- 是否有状态@CouponsStatus INT --优惠券状态)AS----------------------------------------定义参数--------------------------------------declare @strSql NVARCHAR(max);DECLARE @IsUseCount INTDECLARE @ExpiredCount INTDECLARE @NoUseCount INTDECLARE @where NVARCHAR(100);set nocount on;----------------------------------------SQL开始--------------------------------------IF @HasStatus=1BEGINSET @where='m.[State]=@CouponsStatus';ENDELSEBEGINSET @where='1=1'ENDIF @IsGetTotalInfo=0BEGINSET @strSql=N'SELECT DISTINCT t.* FROM (SELECT m.[State] AS [STATUS],m.CouponCode AS CouponsCode,m.CampaignID AS CampaignID,c.Code as CampaignCode,c.Name AS CampaignName,b.ValidityStartTime AS CampaignStartTime,b.ValidityEndTime AS CampaignEndTime,c.Price as CouponsAmount,(CASE WHEN c.IsLimited =1 THEN 1 ELSE 2 END ) as IsLimited,c.FullAmount as MinAmount,e.[Type] AS CouponsType,(CASE WHEN b.IconUrl IS NULL THEN N'''' WHEN b.IconUrl=N'''' THEN N'''' ELSE @hostName+b.IconUrl END) AS IconUrlFROM Loy_MemberCoupon m WITH ( NOLOCK ) INNER JOIN [dbo].[MK_Campaign] AS a WITH ( NOLOCK ) ON m.CampaignID=a.ID AND m.MemberID=@MemberID AND '+@where+' LEFT OUTER JOIN [dbo].[MK_CouponConfig] AS b WITH ( NOLOCK ) ON a.[ID] = b.[CampaignID] LEFT OUTER JOIN [dbo].[MK_Coupon] AS c WITH ( NOLOCK ) ON b.[CouponID] = c.[ID] LEFT OUTER JOIN [dbo].[MK_CouponRestriction] AS d WITH ( NOLOCK ) ON c.[ID] = d.[CompainID] LEFT OUTER JOIN [dbo].[MK_CouponRestrictCategory] AS e WITH ( NOLOCK ) ON d.[ID] = e.[CouponRestrictionID] ) t ORDER BY t.CampaignEndTimeoffset (@PageIndex-1)*@PageSize ROWS FETCH NEXT @PageIndex*@PageSize ROWS ONLY'exec sp_executesql @strSql,N'@PageIndex int,@PageSize int,@hostName nvarchar(100),@MemberID UNIQUEIDENTIFIER,@where NVARCHAR(100),@CouponsStatus int',@PageIndex=@PageIndex,@PageSize=@PageSize,@hostName=@hostName,@MemberID=@MemberID,@where=@where,@CouponsStatus=@CouponsStatusENDELSEBEGIN-------------------------------------------------------------SELECT @IsUseCount=COUNT(1) FROM (SELECT DISTINCT m.CouponCodeFROM Loy_MemberCoupon m WITH ( NOLOCK ) WHERE m.MemberID=@MemberID AND m.[State]=2 ) tSELECT @ExpiredCount=COUNT(1) FROM (SELECT DISTINCT m.CouponCodeFROM Loy_MemberCoupon m WITH ( NOLOCK ) WHERE m.MemberID=@MemberID AND m.[State]=3 ) tSELECT @NoUseCount=COUNT(1) FROM (SELECT DISTINCT m.CouponCodeFROM Loy_MemberCoupon m WITH ( NOLOCK ) WHERE m.MemberID=@MemberID AND m.[State]=1 ) tSELECT @IsUseCount AS IsUseCount,@ExpiredCount AS ExpiredCount,@NoUseCount AS NoUseCountEND----------------------------------------SQL结束--------------------------------------set nocount off;
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