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Editorial Team
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Asked: 2026-05-26T14:11:34+00:00

The following MySQL query completes in under 0.02 seconds : SELECT * FROM `Table1`

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The following MySQL query completes in under 0.02 seconds:

 SELECT
    *
 FROM
    `Table1`
 WHERE
    `col1`     = '43532' AND
    `col2`     = 'N'
 ORDER BY col3 DESC

However, if I add LIMIT 0, 5 at the end of it, it completes in over 7 seconds:

 SELECT
    *
 FROM
    `Table1`
 WHERE
    `col1`     = '43532' AND
    `col2`     = 'N'
 ORDER BY col3 DESC 
 LIMIT 0, 5

This is happening even when the query returns an empty result set.

Why is the addition of LIMIT 0, 5 causing this simple query to be 350 times slower? I need to be able to limit the results for pagination reasons, so how can I fix this?

EDIT:

WITHOUT LIMIT, EXPLAIN says:

id  select_type table   type    possible_keys   key     key_len   ref     rows  Extra
1   SIMPLE      Table1  ref     col1,col2       col1    5         const   2441  Using where; Using filesort

WITH LIMIT, EXPLAIN says:

id  select_type table   type    possible_keys   key   key_len   ref   rows  Extra
1   SIMPLE      Table1  index   col1,col2       col3  5         NULL  1050  Using where
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1 Answer

  1. Editorial Team

    The problem is that the limit causes MySQL to order the query first, forcing it to order the whole set, and then filter it, not using indexes.

    There are directives to tell MySQL which index to use, but it may be better to create a combined index on col1, col2 and col3. MySQL should use that index for filtering and sorting. You should experiment to see whether the query is faster if col3 is the first or the last column in that index.

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