问题描述

我已经有这个问题几个星期了.问题是查询在网站上运行需要 4-5 分钟，而在 ssms 中运行最多需要 2 或 3 秒.我还发现，在更改此查询(例如添加 customerId 变量)后，它将开始在网页上快速运行，但到第二天又变慢了.有问题的查询是这个:

I have been having this problem for a couple of weeks now. The problem is that the query takes 4-5 minutes to run on the website and at most 2 or 3 seconds to run in ssms. Also I found that after I make a change to this query like adding the customerId variable it will start running quickly on the web page but by the next day it is slow again. The query in question is this one:

DECLARE @customerID INT
SET @customerID = @CustID
DECLARE @MyTable table(
Iden int NOT NULL IDENTITY(1,1),
ProductID int)

INSERT INTO @MyTable(ProductID)
SELECT P.ProductID FROM Product P WITH (NOLOCK)
left join Compunix_ProductMMY cpmmy with (nolock) on p.ProductID = cpmmy.ProductID
left join Compunix_CustomerMMY ccmmy with (nolock) on ccmmy.mmyid = cpmmy.mmyid
WHERE P.Deleted=0 AND P.Published=1 and (ccmmy.customerid = @customerID OR cpmmy.productid IS NULL)

SELECT c.Name, c.SeName, c.CategoryID
FROM Category c WITH (NOLOCK) 
JOIN ProductCategory PC With (NOLOCK) ON C.CategoryID = PC.CategoryID
JOIN @MyTable MT ON PC.ProductID=MT.ProductID
WHERE C.Published = 1
GROUP BY c.Name, c.SeName, c.CategoryID
ORDER BY c.Name

我在其他 2 个网站上运行相同的查询，效果很好.站点之间的唯一区别是它们在不同的数据库上运行，与其他两个站点相比，慢站点上的产品(54000 个产品)多一倍多.所有三个站点及其数据库都托管在同一台机器上.

I have the same query running on 2 other site which work just fine. The only difference between the sites is that they are run on different databases and the slow site has a bit more than double the products (54000 products) on it compared to the other 2. All three sites and their databases are hosted on the same machine.

推荐答案

您可能遇到了参数嗅探的问题.

Chances are that you are hitting on a problem with parameter sniffing.

我建议阅读 Erland Sommarskog 的 应用程序慢，SSMS 快? 以获得完整的对问题的理解(文章很长，但很好).

I suggest reading Slow in the Application, Fast in SSMS? by Erland Sommarskog to get a full understanding of the issue (long article but very good).

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