Migração T-SQL da consulta SQL do Access em funcionamento com um problema ao escrever a substituição CASE para IIF
Pergunta
Eu tenho duas mesas BMReports_FPN_Curves e BMReports_BOA_Curves cada um consistindo em um Nome, Data e Hora, Período e Valor, por exemplo:
BM_UNIT_NAME RunDate Period FPN (or BOA)
T_DRAXX-1 2010-12-01 00:03:00 1 497
Com o campo RunDate aumentando em um minuto (isto é c.1440 registros por dia) e os Períodos sendo 1-48.Em BMReports_FPN_Curves Eu tenho um conjunto de dados completo para cada período de tempo e BMReports_BOA_Curves contém os valores que substituirão esses valores base.
Geralmente há valores BOA duplicados e uma instrução IIF aninhada no Acesso A instrução SQL continha uma regra para escolher um entre o FPN, o valor máximo do BOA ou o valor mínimo do BOA para qualquer momento.A regra afirmava:
1) Se não houver valor BOA, use o valor FPN
2) Se houver um valor BOA e for menor que o FPN, encontre e use o valor Min BOA
3) Se houver um valor BOA e for maior que o FPN, encontre e use o valor Max BOA
O Acessar consulta SQL funciona perfeitamente e é o seguinte:
SELECT
dbo_BMReports_FPN_Curves.BM_Unit_Name,
dbo_BMReports_FPN_Curves.RunDate,
dbo_BMReports_FPN_Curves.Period,
dbo_BMReports_FPN_Curves.PN_Level,
IIf(IIf(Min([dbo_BMReports_BOA_Curves]![PN_Level]) <[dbo_BMReports_FPN_Curves]![PN_Level],Min([dbo_BMReports_BOA_Curves]! [PN_Level]),Max([dbo_BMReports_BOA_Curves]![PN_Level])) Is Null, [dbo_BMReports_FPN_Curves]![PN_Level],
IIf(Min([dbo_BMReports_BOA_Curves]![PN_Level])<[dbo_BMReports_FPN_Curves]! [PN_Level],Min([dbo_BMReports_BOA_Curves]! [PN_Level]),Max([dbo_BMReports_BOA_Curves]![PN_Level]))) AS BOA
FROM dbo_BMReports_FPN_Curves LEFT JOIN dbo_BMReports_BOA_Curves ON (dbo_BMReports_FPN_Curves.RunDate = dbo_BMReports_BOA_Curves.RunDate) AND (dbo_BMReports_FPN_Curves.BM_Unit_Name = dbo_BMReports_BOA_Curves.BM_Unit_Name)
GROUP BY dbo_BMReports_FPN_Curves.BM_Unit_Name, dbo_BMReports_FPN_Curves.RunDate, dbo_BMReports_FPN_Curves.Period, dbo_BMReports_FPN_Curves.PN_Level
HAVING (((dbo_BMReports_FPN_Curves.BM_Unit_Name)='T_DRAXX-1'));
Reescrevi a maior parte da consulta em T-SQL (consultando a mesma fonte de dados do SQL Server) e tenho os elementos LEFT JOIN, GROUP BY e HAVING funcionando, mas estou ficando preso na substituição CASE WHEN do IFF e realmente apreciaria uma ajuda se alguém tivesse alguns momentos de sobra.
A consulta SQL como está atualmente:
SELECT
BMReports_FPN_Curves.BM_Unit_Name,
BMReports_FPN_Curves.RunDate,
BMReports_FPN_Curves.Period,
AVG(BMReports_FPN_Curves.PN_Level) AS FPN,
CASE
WHEN BMReports_BOA_Curves.PN_Level IS NULL THEN AVG(BMReports_FPN_Curves.PN_Level)
WHEN MIN(BMReports_BOA_Curves.PN_Level) IS < AVG(BMReports_FPN_Curves.PN_Level) THEN MIN(BMReports_BOA_Curves.PN_Level)
ELSE MAX(BMReports_BOA_Curves.PN_Level)
END AS BOA
FROM BMReports_FPN_Curves
LEFT JOIN BMReports_BOA_Curves ON BMReports_FPN_Curves.BM_Unit_Name = BMReports_BOA_Curves.BM_Unit_Name
AND BMReports_FPN_Curves.RunDate = BMReports_BOA_Curves.RunDate
GROUP BY BMReports_FPN_Curves.BM_Unit_Name, BMReports_FPN_Curves.RunDate, BMReports_FPN_Curves.Period
HAVING BMReports_FPN_Curves.BM_Unit_Name = 'T_DRAXX-1'
ORDER BY BMReports_FPN_Curves.BM_Unit_Name, BMReports_FPN_Curves.RunDate, BMReports_FPN_Curves.Period
Solução
SELECT fc.BM_Unit_Name
, fc.RunDate
, fc.Period
, CASE
WHEN AVG(bc.PN_Level) IS NULL THEN AVG(fc.PN_Level) -- No BOA Value, use the FPN Value
WHEN MIN(bc.PN_Level) < AVG(fc.PN_Level) THEN MIN(bc.PN_Level) -- BOA Value is less than the FPN, use the BOA Value
ELSE MAX(bc.PN_Level) -- BOA Value is greater than the FPN, use the BOA Value
END
FROM dbo.BMReports_FPN_Curves fc
LEFT JOIN dbo.BMReports_BOA_Curves bc ON fc.RunDate = bc.RunDate
AND fc.BM_Unit_Name = bc.BM_Unit_Name
WHERE fc.BM_Unit_Name ='T_DRAXX-1'
GROUP BY
fc.BM_Unit_Name
, fc.RunDate
, fc.Period
Outras dicas
Provavelmente é melhor usar um CTE para fazer todos os cálculos agregados e depois fazer a declaração do caso com base nisso.
WITH cte
AS (SELECT bmreports_fpn_curves.bm_unit_name,
bmreports_fpn_curves.rundate,
bmreports_fpn_curves.period,
AVG(bmreports_fpn_curves.pn_level) AS fpn,
AVG(bmreports_fpn_curves.pn_level) AS boa,
MIN(bmreports_boa_curves.pn_level) minboa,
MAX(bmreports_fpn_curves.pn_level) maxfpn
FROM bmreports_fpn_curves
LEFT JOIN bmreports_boa_curves
ON bmreports_fpn_curves.bm_unit_name =
bmreports_boa_curves.bm_unit_name
AND bmreports_fpn_curves.rundate =
bmreports_boa_curves.rundate
GROUP BY bmreports_fpn_curves.bm_unit_name,
bmreports_fpn_curves.rundate,
bmreports_fpn_curves.period
HAVING bmreports_fpn_curves.bm_unit_name = 'T_DRAXX-1')
SELECT bm_unit_name,
rundate,
period ,
CASE
WHEN BOA IS NULL THEN FPN
WHEN BOA < FPN THEN MinBoa
WEHN BOA > FPN THEN MaxBoa
ELSE -- BOA = FPN THEN WHAT?
END as BOA
FROM cte
Para bancos de dados que não suportam CTEs, você também pode usar um select dentro de from (visualização inline).Aliás, o Access suporta isso.
SELECT bm_unit_name,
rundate,
period ,
CASE
WHEN BOA IS NULL THEN FPN
WHEN BOA < FPN THEN MinBoa
WEHN BOA > FPN THEN MaxBoa
ELSE -- BOA = FPN THEN WHAT?
END as BOA
FROM (
SELECT bmreports_fpn_curves.bm_unit_name,
bmreports_fpn_curves.rundate,
bmreports_fpn_curves.period,
AVG(bmreports_fpn_curves.pn_level) AS fpn,
AVG(bmreports_fpn_curves.pn_level) AS boa,
MIN(bmreports_boa_curves.pn_level) minboa,
MAX(bmreports_fpn_curves.pn_level) maxfpn
FROM bmreports_fpn_curves
LEFT JOIN bmreports_boa_curves
ON bmreports_fpn_curves.bm_unit_name =
bmreports_boa_curves.bm_unit_name
AND bmreports_fpn_curves.rundate =
bmreports_boa_curves.rundate
GROUP BY bmreports_fpn_curves.bm_unit_name,
bmreports_fpn_curves.rundate,
bmreports_fpn_curves.period
HAVING bmreports_fpn_curves.bm_unit_name = 'T_DRAXX-1') ) t
Você já tentou uma tradução mais literal do IIF para CASE?Por exemplo, sua cadeia IIF se parece com isto:
IIf
(
IIf
(
Min([dbo_BMReports_BOA_Curves]![PN_Level]) < [dbo_BMReports_FPN_Curves]![PN_Level],
Min([dbo_BMReports_BOA_Curves]![PN_Level]),
Max([dbo_BMReports_BOA_Curves]![PN_Level])
) Is Null,
[dbo_BMReports_FPN_Curves]![PN_Level],
IIf
(
Min([dbo_BMReports_BOA_Curves]![PN_Level]) < [dbo_BMReports_FPN_Curves]![PN_Level],
Min([dbo_BMReports_BOA_Curves]![PN_Level]),
Max([dbo_BMReports_BOA_Curves]![PN_Level])
)
) AS BOA
Portanto, uma tradução literal seria algo assim:
(
case
when
(
case
when Min(BMReports_BOA_Curves.PN_Level) < BMReports_FPN_Curves.PN_Level then
Min(BMReports_BOA_Curves.PN_Level)
else
Max(BMReports_BOA_Curves.PN_Level)
end
) is null then
BMReports_FPN_Curves.PN_Level
else
(
case
when Min(BMReports_BOA_Curves.PN_Level) < BMReports_FPN_Curves.PN_Level then
Min(BMReports_BOA_Curves.PN_Level)
else
Max(BMReports_BOA_Curves.PN_Level)
end
)
end
) as BOA
Não tenho acesso ao seu esquema completo nem aos dados, por isso não posso testar a tradução, mas acredito que esteja sintaticamente correta.