For loop inside SQL query - php

Question

I have a table named watersourcetype consisting of water types.
link : watersourcetype TABLE
and another table health_and_sanitation consisting of household no. and watersource_id
I have this query :
SELECT h.purok_number,
SUM(CASE WHEN hs.watersystem = 'Community water system-own' THEN 1 ELSE 0 END) AS a,
SUM(CASE WHEN hs.watersystem = 'Community water system-shared' THEN 1 ELSE 0 END) AS b,
SUM(CASE WHEN hs.watersystem = 'Deep well-own' THEN 1 ELSE 0 END) AS c,
SUM(CASE WHEN hs.watersystem = 'Deep well-shared' THEN 1 ELSE 0 END) AS d,
SUM(CASE WHEN hs.watersystem = 'Artesian well-own' THEN 1 ELSE 0 END) AS e,
SUM(CASE WHEN hs.watersystem = 'Artesian well-shared' THEN 1 ELSE 0 END) AS f,
SUM(CASE WHEN hs.watersystem = 'Dug/shallow well-own' THEN 1 ELSE 0 END) AS g,
SUM(CASE WHEN hs.watersystem = 'Dug/shallow well-shared' THEN 1 ELSE 0 END) AS h,
SUM(CASE WHEN hs.watersystem = 'River, stream, lake, spring, bodies of water' THEN 1 ELSE 0 END) AS i,
SUM(CASE WHEN hs.watersystem = 'Bottled water' THEN 1 ELSE 0 END) AS j,
SUM(CASE WHEN hs.watersystem = 'Tanker truck/Peddler' THEN 1 ELSE 0 END) AS k
FROM health_and_sanitation AS hs, house_hold AS h, f_member as f
WHERE
h.brgy_name='$brgy_name' AND
h.hh_number=hs.hh_number AND
h.hh_number=f.hh_number AND
f.is_household='HOUSEHOLD' AND
EXTRACT(YEAR FROM f.reg_date) BETWEEN '$sel_year' AND '$sel_year'
group by h.purok_number
order by h.purok_number
what i want is to put a for loop inside above sql query since table watersourcetype is dynamic another data will be added to watersourcetype soon so i dont have to define in my case statement on above query the watersystem . The query should look like this :
$qry = pg_query("select cwatertype from tbl_watersourcetype");
SQL:
SELECT h.purok_number,
// is this possible ? putting a while loop or forloop inside a query in PHP ?
while($row = pg_fetch_array($qry))
{
SUM(CASE WHEN hs.watersystem = '$row['cwatertype']' THEN 1 ELSE 0 END) AS a
}
FROM health_and_sanitation AS hs, house_hold AS h, f_member as f
WHERE
h.brgy_name='$brgy_name' AND
h.hh_number=hs.hh_number AND
h.hh_number=f.hh_number AND
f.is_household='HOUSEHOLD' AND
EXTRACT(YEAR FROM f.reg_date) BETWEEN '$sel_year' AND '$sel_year'
group by h.purok_number
order by h.purok_number
is that possible ?

Answer 1

If I understand your query correctly, you are trying to retrieve the number of watersourcetypes per household, with a single record returned per household. If that is indeed the case you need to use the crosstab() function from the tablefunc extension.
However, if you can get by with multiple rows giving the number of sources per watersourcetype per household then you can simply and more efficiently use the COUNT() aggregate in the SELECT statement (with some decent formatting for legibility):
SELECT h.purok_number, hs.watersystem, COUNT(hs.watersystem) AS num
FROM health_and_sanitation AS hs,
house_hold AS h,
f_member AS f
WHERE h.brgy_name='$brgy_name'
AND h.hh_number=hs.hh_number
AND h.hh_number=f.hh_number
AND f.is_household='HOUSEHOLD'
AND EXTRACT(YEAR FROM f.reg_date) BETWEEN '$sel_year' AND '$sel_year'
GROUP BY h.purok_number, hs.watersystem
ORDER BY h.purok_number;
Additionally, I am assuming that your health_and_sanitation table is a view on the watersourcetype table; otherwise you are duplicating data in two tables which is (generally) a big boo-boo. Given also your issue with additional water source type, you may want to see if your database design is in 3NF.
Cheers,
Patrick

Answer 2

this is an example on how to put for loop inside SELECT statement :
$qry_6_12 .= " SELECT count(ncropfarmingreasonid) as counted , " ;
for($i=2;$i<=$count_row;$i++) // loop the number of rows and used $i as ncropfarmingreasonid
{
if(($count_row-$i)==0)
{
$qry_6_12 .= "SUM(CASE WHEN ncropfarmingreasonid = ".$i." THEN 1
ELSE 0 END) a".$i."";
}
else
{
$qry_6_12 .= "SUM(CASE WHEN ncropfarmingreasonid = ".$i." THEN 1
ELSE 0 END) a".$i.",";
}
}
$qry_6_12 .= " FROM tbl_climatechange as c, tbl_household as h, tbl_barangay as b where h.chholdnumber=c.chholdnumber and b.cbrgycode=h.cbrgycode and b.cbrgyname = 'AMPAYON' ";
$query_6_12 = pg_query($qry_6_12);