Solved

MySQL JOIN Clause

Posted on 2014-12-03
3
488 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 10

Accepted Solution

by:
JEaston earned 250 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 250 total points
ID: 40478254
I agree 100%: the presence of indexes will not change the data returned, only the speed
0
 
LVL 110

Author Closing Comment

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

Featured Post

Microsoft Certification Exam 74-409

Veeam® is happy to provide the Microsoft community with a study guide prepared by MVP and MCT, Orin Thomas. This guide will take you through each of the exam objectives, helping you to prepare for and pass the examination.

Question has a verified solution.

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

Suggested Solutions

If you have heard of RFC822 date formats, they can be quite a challenge in SQL Server. RFC822 is an Internet standard format for email message headers, including all dates within those headers. The RFC822 protocols are available in detail at:   ht…
Composite queries are used to retrieve the results from joining multiple queries after applying any filters. UNION, INTERSECT, MINUS, and UNION ALL are some of the operators used to get certain desired results.​
In a recent question (https://www.experts-exchange.com/questions/29004105/Run-AutoHotkey-script-directly-from-Notepad.html) here at Experts Exchange, a member asked how to run an AutoHotkey script (.AHK) directly from Notepad++ (aka NPP). This video…

730 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