Output of 3 queries - mysql

Question

Got this 3 in 1 query:
SELECT * FROM
(
SELECT mesures.date j, AVG(mesures.valeur) maxi
FROM mesures
JOIN plages_horaire ON mesures.id_plage = plages_horaire.id_plage
WHERE MONTH(mesures.date) = '9' AND YEAR(mesures.date) = '2016' AND mesures.code_station = 'P02SE' AND mesures.id_crit = '1' AND mesures.id_type = '1'
GROUP BY mesures.date
) maxi
,
(
SELECT AVG(mesures.valeur) mini
FROM mesures
JOIN plages_horaire ON mesures.id_plage = plages_horaire.id_plage
WHERE MONTH(mesures.date) = '9' AND YEAR(mesures.date) = '2016' AND mesures.code_station = 'P02SE' AND mesures.id_crit = '1' AND mesures.id_type = '2'
GROUP BY mesures.date
) mini
,
(
SELECT AVG(mesures.valeur) moy
FROM mesures
JOIN plages_horaire ON mesures.id_plage = plages_horaire.id_plage
WHERE MONTH(mesures.date) = '9' AND YEAR(mesures.date) = '2016' AND mesures.code_station = 'P02SE' AND mesures.id_crit = '1' AND mesures.id_type = '3'
GROUP BY mesures.date
) moy
GROUP BY j
Problem is that I get what I want excepting values of the 2 last columns are the same at every rows:
query output
I believe it's because of the GROUP BY.

Answer 1

From what I can see from your query, you don't need the plage_horaire table. You can also simplify the logic greatly by using conditional aggregation:
SELECT m.date,
AVG(CASE WHEN m.id_type = 1 THEN m.valeur END) maxi,
AVG(CASE WHEN m.id_type = 2 THEN m.valeur END) mini,
AVG(CASE WHEN m.id_type = 3 THEN m.valeur END) maxmoy,
FROM mesures m
WHERE MONTH(m.date) = 9 AND YEAR(m.date) = 2016 AND
m.code_station = 'P02SE' AND m.id_crit = 1 AND m.id_type IN (1, 2, 3)
GROUP BY m.date ;
Notice that I also removed the quotes from the numeric constants. MONTH() and YEAR() return numbers, so quotes are not appropriate. I am guessing that the ids are numeric as well.