Hello,
I am relatively new to MySQL though I have database experience.
I have a query that doesn't seem to want to use an index for the first
table despite my indexing several fields. Before I get too far in the
details of the query, here is what EXPLAIN SELECT tells me for the
first table of the LEFT JOIN:
type=ALL
possible_keys=NULL
extra=where used; using temporary; using filesort
I found a reference that usage of a temporary table "...typically
happens if you do an ORDER BY on a different column set than you did a
GROUP BY on." This is the case as my ORDER BY uses two columns while I
group on one. Does that preclude the use of an index?
Also, my first table has about 65 rows, and about 95% are used
for the query (as limited by a WHERE condition), though any number of
rows will be returned. Given that is the case, would that prevent
MySQL from using an index? Or does it even matter with a table this
size? For the record, it's the second table that has several thousand
rows, and MySQL uses an index for that table in this query.
- Steve Yates
- if (stone != rolling) moss++;
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