PostgreSQL: how to convert "PIVOT" from T-SQL to PLPGSQL procedure - postgresql

Question

I would like to convert a stored procedure from T-SQL to PL/PGSQL.
Here is the T-SQL code
SELECT NO_PTF, coalesce(1, 0) as RISK_1, coalesce(2, 0) as RISK_2, coalesce(3, 0) as RISK_3, coalesce(4, 0) as RISK_4
FROM (
SELECT D.NO_PTF, C.NB_DEG_RSQ, D.MT_DEM/100 as MT_DEM
FROM public.TB_Demande D
INNER JOIN
public.TB_Compartiment C ON D.ID_CPA = C.ID_CPA
AND D.MC_UTL = 'F3000'
AND C.IN_ACT = true
) Q
PIVOT (SUM(Q.MT_DEM) FOR Q.NB_DEG_RSQ IN (1, 2, 3, 4)) as PVT
)
I tried to replace PIVOT by crosstab. But i have an error. Here is my PL/PGSQL code
SELECT NO_PTF, coalesce(1, 0) as RISK_1, coalesce(2, 0) as RISK_2, coalesce(3, 0) as RISK_3, coalesce(4, 0) as RISK_4
FROM (
SELECT D.NO_PTF, C.NB_DEG_RSQ, D.MT_DEM/100 as MT_DEM
FROM public.TB_Demande D
INNER JOIN
public.TB_Compartiment C ON D.ID_CPA = C.ID_CPA
AND D.MC_UTL = 'F3000'
AND C.IN_ACT = true
) Q
crosstab (SUM(Q.MT_DEM) FOR Q.NB_DEG_RSQ IN (1, 2, 3, 4)) as PVT
Someone have an idea about the rigth way to use crosstab here?

Answer 1

I am not entirely sure I understand the PIVOT syntax, but typically this is way easier in Postgres using a filtered aggregation, not the somewhat clumsy crosstab() function.
I think this should be equivalent:
select no_ptf,
sum(mt_dem) filter (where NB_DEG_RSQ = 1) as risk_1,
sum(mt_dem) filter (where NB_DEG_RSQ = 2) as risk_2,
sum(mt_dem) filter (where NB_DEG_RSQ = 3) as risk_3,
sum(mt_dem) filter (where NB_DEG_RSQ = 4) as risk_4
from (
SELECT D.NO_PTF, C.NB_DEG_RSQ, D.MT_DEM/100 as MT_DEM
FROM public.TB_Demande D
INNER JOIN public.TB_Compartiment C
ON D.ID_CPA = C.ID_CPA
AND D.MC_UTL = 'F3000'
AND C.IN_ACT = true
)
GROUP BY no_ptf;