如何优化sql查询 [英] how to optimize sql query

问题描述

哪一个更快？加入还是子查询？

Which one is faster? Join or Subquery?

推荐答案

这取决于很多因素。请参阅过去的答案和CP知识库文章 [ ^ ]。

It depends on many factors. Please, see past answers and CP Knowledge Base articles[^].

没有明确的答案。通常在SQL Server中，您可以加入，但在Oracle中，您将使用子查询。每个DBMS都旨在优化这种方式，但并非总是如此。以下是一些关于如何使用SQL Server执行计划来测试JOIN和子查询的性能的很好的例子。如果你从未使用过它。



http://blog.sqlauthority.com/2010/06/06/sql-server-subquery-or-join-various -options-sql-server-engine-knows-the-best / [ ^ ]



http://sqlstudies.com/2013/05/02 /比较内部联接与子查询/ [ ^ ]

There is no clear cut answer. Typically in SQL Server you would you JOINs, but in Oracle you'd use Subqueries. The each DBMS is designed to optimize that way, but it isn't always true. Here are a couple of nice examples on how to use the SQL Server Execution Plan to test performance of JOINs and Subqueries; if you've never used that.

http://blog.sqlauthority.com/2010/06/06/sql-server-subquery-or-join-various-options-sql-server-engine-knows-the-best/[^]

http://sqlstudies.com/2013/05/02/comparing-an-inner-join-vs-a-subquery/[^]

您好，



检查这个...



加入Vs子查询 [ ^ ]



希望这会对你有所帮助。



干杯

Hi,

Check this...

Joins Vs Subqueries[^]

Hope this will help you.

Cheers

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