如何用合并联接替换哈希匹配? [英] How to replace Hash Match with Merged Join?

问题描述

我正在学习SQL Server联接操作的工作方式，并且正在使用Adventure Works 2017 db.

I'm learning how SQL Server join operations works and I'm working on Adventure Works 2017 db.

这是我的查询:

SELECT 
   e.JobTitle, a.City,
   p.LastName + ', ' + p.FirstName AS EmployeeName
FROM HumanResources.Employee AS e
INNER JOIN Person.BusinessEntityAddress AS bea
   ON e.BusinessEntityID = bea.BusinessEntityID
INNER JOIN Person.Address AS a
   ON bea.AddressID = a.AddressID
INNER JOIN Person.Person AS p
   ON e.BusinessEntityID = p.BusinessEntityID

执行计划:

我的问题是我该怎么办才能用合并联接替换哈希匹配操作?

My question is what can I do to replace Hash Match operation with Merged Join?

推荐答案

您可以指定请记住，在SQL Server中，提示被认为是不得已的措施.最好查看索引碎片级别，然后在查询中添加提示.

Keep in mind that, in SQL Server, hints are considered measures of a last resort. It's much better to look at missing indices and / or index fragmentation levels before nailing a hint into a query.

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