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What's the sort order on a MySql database if you don't specify one?

Posted on 2010-09-21
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What does a MySQL database sort by when you don't specify anything. In other words, if you just ask for an array with no sorting criteria at all, in what order does it provide the data?
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Question by:brucegust
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8 Comments
 

Author Comment

by:brucegust
ID: 33730810
Head out to http://www.elivestockauctions.com/auctions/preview. There's an array being created using a JQuery approach and since there's no sort functionality offered natively, I'm trying to figure out how the data is being presented so I can hot wire some things and provide the user with a logical sequence.
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Accepted Solution

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Ephraim Wangoya earned 500 total points
ID: 33730854
Its in the order in which it is inserted in the table if there is no index defined
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Author Comment

by:brucegust
ID: 33730972
The id is the Primary field with four other fields listed as indexes.

When I sort by the "created_date," that's not the order in which the data is displayed. But when I hit "Browse" in my phpMyAdmin, the order in which that data is displayed is exactly the way it shows up on the page.

What can I do to figure out the way in which the system is sorting this?
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LVL 3

Assisted Solution

by:celdridgeMadman
celdridgeMadman earned 1000 total points
ID: 33731010
Depends on the table type as well. InnoDB will store records in the order of the Primary Key, whilst MyISAM will store them in the order entered.
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Assisted Solution

by:rstjean
rstjean earned 500 total points
ID: 33731034
Try using the explain command.

EXPLAIN SELECT * FROM animals.  can run this from phpmyadmin.

If you have a problem with indexes not being used when you believe that they should be, you should run ANALYZE TABLE
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Author Comment

by:brucegust
ID: 33731067
Here's what I get when I run "EXPLAIN..."

id  select_type  table  type  possible_keys  key  key_len  ref  rows  Extra  
1 SIMPLE lots ALL NULL NULL NULL NULL 66  
 
What does that mean as far as how data is being sorted?

As far as the table type, how would I figure that out?

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LVL 3

Assisted Solution

by:celdridgeMadman
celdridgeMadman earned 1000 total points
ID: 33731109
the query SHOW TABLE STATUS FROM tblname shoudl return that information for you. Provided you have the necessary permissions. If not you'll need to get the DBA for that server to obtain it for you.
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Author Closing Comment

by:brucegust
ID: 33775047
This answered my question.
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