# For good performance Join values or direct values?

**URL:** <https://forums.percona.com/t/for-good-performance-join-values-or-direct-values/1167>\
**Category:** Other MySQL® Questions\
**Created:** [May 11, 2009, 3:26am UTC](https://forums.percona.com/t/for-good-performance-join-values-or-direct-values/1167 "2009-05-11T03:26:57Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![phparmy](https://avatars.discourse-cdn.com/v4/letter/p/c2a13f/32.png) [@phparmy](https://forums.percona.com/u/phparmy)\
**Post date:** [May 11, 2009, 3:26am UTC](https://forums.percona.com/t/for-good-performance-join-values-or-direct-values/1167/1 "2009-05-11T03:26:57Z")

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hello,

assume i have two tables

Table 1 courses

course\_id,title

Table 2 scores

user\_id,course\_id,grade

i have a variable course\_id is 2

i have two queries which one of them have good performance?

Query 1  
select courses.title,scores.grade from courses,scores where courses.course\_id=‘2’ and scores.course\_id=‘2’

Query 2  
select courses.title,scores.grade from courses,scores where courses.course\_id=‘2’ and scores.course\_id=courses.course\_id

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**Author:** ![sterin71](https://avatars.discourse-cdn.com/v4/letter/s/5e9695/32.png) [@sterin71](https://forums.percona.com/u/sterin71)\
**Post date:** [May 11, 2009, 5:52am UTC](https://forums.percona.com/t/for-good-performance-join-values-or-direct-values/1167/2 "2009-05-11T05:52:02Z")

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You should always use Query 2.

There is no performance difference between them because the value is known in advance. But in query 2 you explicitly show whoever is reading the code that there is a relation between the two tables.

But please see my post on your other question regarding the use of INNER JOIN syntax to further improve on writing your queries easily understandable and reduce risk for bugs.