Re: Another newbie question
Posted by:
Rick James
Date: February 13, 2014 11:10PM
> EXPLAIN is below, although it seems to contain the same information as the CREATE TABLE command.
EXPLAIN SELECT ...
> or is it only effective when my query includes all 3 fields in the index?
It is useful for any _left_ prefix. That is,
INDEX(a,b,c)
is useful for
WHERE a=1
WHERE b=1 AND a=2
WHERE a=11 AND c=33 AND b=99
But not
WHERE b=1 (without a)
etc.
> KEY `fk_QSO_User_idx` (`clientID`),
is useless, because there is another index that starts with that. (actually 2 other indexes).
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Re: Another newbie question
February 13, 2014 11:10PM
February 16, 2014 12:51AM
February 27, 2014 04:54AM
February 27, 2014 08:47PM