mysql grouping mre than one query - mysql

Question

I try to explain the matter:
I have a hotel management system built with php+mysql.
I need to extract the number of:
current reservations visitors
arriving visitors
leaving visitors
and I need to know this numbers grouped by "region" (Region is either a country or a region of a country. I get this info from a stored function).
I have tried many times, but I always get values not in line with what I expect.
I have tried grouping by sum, by region, by the two of them, I have tried nesting the queries (horrible result...i'm not that good at subqueries).
Here are the 3 main queries:
Current visitors:
select p.num_persone, IFNULL(getcoderegione(c.regione),getNazioneCodeIstat(c.nazione)) regione, p.*, c.nazione, c.regione from prenota2015 p INNER JOIN clienti c ON c.idclienti = p.idclienti where p.iddatainizio < 94 and p.iddatafine >= 93 and p.idclienti != '0';
Arriving visitors:
select p.num_persone, IFNULL(getcoderegione(c.regione),getNazioneCodeIstat(c.nazione)) regione, p.*, c.nazione, c.regione from prenota2015 p INNER JOIN clienti c ON c.idclienti = p.idclienti where p.iddatainizio < 94 and p.iddatainizio >= 93 and p.idclienti != '0';
Leaving visitors:
select p.num_persone, IFNULL(getcoderegione(c.regione),getNazioneCodeIstat(c.nazione)) regione, p.*, c.nazione, c.regione from prenota2015 p INNER JOIN clienti c ON c.idclienti = p.idclienti where p.iddatafine < 93 and p.iddatafine >= 92 and p.idclienti != '0';
The IFNULL stuff checks if it should present the country code or the region code.
Table 'clienti' contains the value of the region or country for IFNULL check mentioned above and it is important for the grouping clause.
what I expect is something like:
| region code | visitors present | visitors arriving | visitors leaving
------------------------------------------------------------------------
| 219 | 3 | 1 | 1 |
------------------------------------------------------------------------
| 186 | 2 | 0 | 0 |
and so on.
Question time: I would you do it?
I tried last time with:
SELECT DISTINCT
IFNULL(getcoderegione(c.regione),getNazioneCodeIstat(c.nazione)) regione,
pres.presenze,
part.partenze,
arr.arrivi
FROM
(
select COUNT(p.idprenota) partenze, p.idclienti
from prenota2015 p
INNER JOIN clienti c ON c.idclienti = p.idclienti
where
p.iddatafine < 91
and p.iddatafine >= 90
GROUP BY regione
) as part,
(
select COUNT(p2.idprenota) arrivi, p2.idclienti
from prenota2015 p2
INNER JOIN clienti c ON c.idclienti = p2.idclienti
where
p2.iddatainizio < 91
and p2.iddatainizio >= 90
GROUP BY regione
) as arr,
(
select COUNT(p3.idprenota) presenze, p3.idclienti
from prenota2015 p3
INNER JOIN clienti c ON c.idclienti = p3.idclienti
where
p3.iddatainizio < 91
and p3.iddatafine >= 90
GROUP BY regione
) as pres,
clienti c
but it was a desperate attempt to try to understand how to move around it.
Any help? Suggestions?
Thank you very much

Answer 1

SELECT q1.regione,
q1.total AS current_visitors,
q2.total AS arriving_visitors,
q1.total AS leaving_visitors
FROM (
SELECT sum(p.num_persone) total,
IFNULL(getcoderegione(c.regione), getNazioneCodeIstat(c.nazione)) regione
FROM prenota2015 p
INNER JOIN clienti c ON c.idclienti = p.idclienti
WHERE p.iddatainizio < 94
AND p.iddatafine >= 93
AND p.idclienti != '0'
GROUP BY regione
) q1
INNER JOIN (
SELECT sum(p.num_persone) total,
IFNULL(getcoderegione(c.regione), getNazioneCodeIstat(c.nazione)) regione
FROM prenota2015 p
INNER JOIN clienti c ON c.idclienti = p.idclienti
WHERE p.iddatainizio < 94
AND p.iddatainizio >= 93
AND p.idclienti != '0'
GROUP BY regione
) q2 ON q1.regione = q2.regione
INNER JOIN (
SELECT sum(p.num_persone) total,
IFNULL(getcoderegione(c.regione), getNazioneCodeIstat(c.nazione)) regione
FROM prenota2015 p
INNER JOIN clienti c ON c.idclienti = p.idclienti
WHERE p.iddatafine < 93
AND p.iddatafine >= 92
AND p.idclienti != '0'
GROUP BY regione
) q3 ON q1.regione = q3.regione;
or, as moo suggested, create views of your three queries, which would make this one a lot neater