New answers tagged mysql-5.5
-1
No one pointed out the actual problem with the Bad code so: You need to name the inner SELECT's output using AS some_name
SELECT COUNT(ip_address) FROM (
SELECT DISTINCT ip_address FROM `ports` WHERE status IS TRUE
) AS some_name
As mentioned already, best is:
SELECT COUNT(DISTINCT ip_address) FROM `ports`;
Why?
See: https://stackoverflow.com/questions/...
-2
my trick is, make temporary table with field category and units then u make schedule at night to counting it n save to your temporary table, then ur just read that table with just 12 row in it, very faster, but ur count H-1, u need liitle trick againt to add current day ...
0
You may use union all to avoid sorting
mysql> select id from (
-> SELECT u.id
-> FROM user u
-> LEFT JOIN translation_revision t1
-> ON u.id = t1.translator_id
->union all
-> SELECT u.id
-> FROM user u
-> LEFT JOIN translation_revision t2
-> ...
2
Instead of doing 3 separate joins, you could accomplish the same thing by simply using an OR clause (the execution time seems to be ~1-2ms):
SELECT DISTINCT u.id
FROM user u
JOIN translation_revision t1
ON u.id = t1.translator_id OR u.id = t1.proofreader_id OR u.id = t1.reviewer_id
GROUP BY u.id
LIMIT 30
Other ideas would be to denormalize your data ...
0
Maybe simply
SELECT DISTINCT u.id
FROM user u
JOIN translation_revision t
ON u.id IN (t.translator_id, t.proofreader_id, t.reviewer_id)
?
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