Question

I want optimize this select:

Select Dane1, Dane5, Dane6, Dane7 FROM Test
INNER JOIN Test2 ON Test.Id=Test2.IdTest
WHERE Dane5 > 199850

My database has 2 tables test, test2:

test design: Id int ->PRIMARY KEY, Dane1 int, Dane2 int, Dane3 int, Dane4 int, Dane5 int,

test2 design: Id int ->PRIMARY KEY, Dane6 int, Dane7 int, IdTest int,

Default index: PK__test__7C8480AE(Clustered), PK__test2__7E6CC920(Clustered)

The question is: Which indexes to attach or remove?

Answer 1

It's always a good idea to define foreign-key relationships. On that way you keep data integrity and you can specify what happens if a parent record is deleted(f.e. delete children recursively).

A foreign-key is also a good candidate for an index to lookup the child-records quickly.

Answer 2

创建索引时需要考虑的一些事项，例如在这种情况下：

Dane5有多少行＆gt; 199850和总共有多少行？
索引中的列是否有很多更新 - ＆gt;更新缓慢。
是否会对基表进行大量的键查找以获取查询中所需的其余列？

您可以尝试这样的事情：

Create index test_xxx on test (Dane5) include (Dane1)

包含Dane1的天气取决于有多少行以及密钥查找是否导致问题

ID已包含在内，因为它是聚集索引

Create index test2_yyy on test2 (IdTest) include (Dane6, Dane7)

将Dane6和Date7作为包含列的天气也取决于需要对表进行的键查找总量以获取它们

您应该打开统计信息io以查看导致最合理读取的原因，以及天气是否需要索引中包含的列。

Answer 3

As Tim pointed out, foreign keys and an index defined on the foreign key is a good call.

One additional index that could get you some additional speed - assuming your where clause is always going to be on Dane5 - is to add a nonclustered index on Dane5

Optimize the execution of select

3 个答案: