?
Solved

MySQL JOIN Clause

Posted on 2014-12-03
3
Medium Priority
?
508 Views
Last Modified: 2014-12-03
Scenario:  I have two MySQL tables.  Both of them have an index on the column called "foo."  

1. I run a SELECT query and use a JOIN clause naming "foo" in the two tables.  I get a results set giving the intersection of the tables on "foo."

2. I remove the index from one or both of the tables and rerun the query in #1.

Will I get the same results set from the second (unindexed) SELECT?  Or does the presence of an index affect the results of JOIN?
0
Comment
Question by:Ray Paseur
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
3 Comments
 
LVL 11

Accepted Solution

by:
John Easton earned 1000 total points
ID: 40478242
If I understand your question correctly, then Yes you should get the same result regardless of whether the joined columns are indexed or not.  Indexed columns are likely to result in a faster query run time - but if the tables are not large then chances are you will not notice the difference.
0
 
LVL 143

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 1000 total points
ID: 40478254
I agree 100%: the presence of indexes will not change the data returned, only the speed
0
 
LVL 111

Author Closing Comment

by:Ray Paseur
ID: 40478269
Thanks, colleagues!
0

Featured Post

What Is Blockchain Technology?

Blockchain is a technology that underpins the success of Bitcoin and other digital currencies, but it has uses far beyond finance. Learn how blockchain works and why it is proving disruptive to other areas of IT.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction This article is intended for those who are new to PHP error handling (https://www.experts-exchange.com/articles/11769/And-by-the-way-I-am-New-to-PHP.html).  It addresses one of the most common problems that plague beginning PHP develop…
It is possible to export the data of a SQL Table in SSMS and generate INSERT statements. It's neatly tucked away in the generate scripts option of a database.
In this video, Percona Solution Engineer Dimitri Vanoverbeke discusses why you want to use at least three nodes in a database cluster. To discuss how Percona Consulting can help with your design and architecture needs for your database and infras…
In this video, Percona Solution Engineer Rick Golba discuss how (and why) you implement high availability in a database environment. To discuss how Percona Consulting can help with your design and architecture needs for your database and infrastr…

800 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question