MySQL Table indexation
I have table with 11 fields. Not i'm making SELECT query to get data for
specific reason.
SELECT `id` FROM `A`
WHERE b IS NOT NULL,
c IS NOT NULL,
d IS NOT NULL
ORDER BY e DESC
I have made index on (b,c,d) AND (e)
MySQL EXPLAIN shows possible_keys that group index, but key NULL, and in
extra section there is - Using where; Using filesort
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