[英]Convert a nested subquery into normal query
我對以下查詢有疑問,其中嵌套查詢應轉換為普通查詢:
select
count(*) as count,
TO_CHAR(RH.updated_datetime,'DD-MM-YYYY HH:MI:SS') as date,
SUM(
extract (
epoch from (
RH.updated_datetime - PRI.procedure_performed_datetime
)
)/60
)::integer/count(*) as diff
from
procedure_runtime_information PRI,
study S,
report R,
report_history RH
where
RH.report_fk = R.pk AND
R.study_fk = S.pk AND
S.procedure_runtime_fk = PRI.pk AND
RH.old_status_fk = 21 AND
RH.revision = (select max(revision) from report_history where RH.report_fk = RH.report_fk) AND
RH.updated_datetime > TO_DATE('22-01-2013 00:00:00', 'DD-MM-YYYY HH24:MI:SS') AND RH.updated_datetime < TO_DATE('22-01-2014 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
group by date order by date asc;
假設這個
(select max(revision) from report_history where RH.report_fk = RH.report_fk)
確實應該是:
(select max(revision) from report_history x where x.report_fk = RH.report_fk)
您可以將嵌套( 相關 )子查詢轉換為普通的子查詢,如下所示(多種方式之一):
SELECT count(*) AS ct
,to_char(rh.updated_datetime,'DD-MM-YYYY HH:MI:SS') AS date -- HH24?
,sum(extract(epoch FROM (RH.updated_datetime
- PRI.procedure_performed_datetime))
/ 60)::int / count(*) AS diff
FROM procedure_runtime_information PRI
JOIN study S ON S.procedure_runtime_fk = PRI.pk
JOIN report R ON R.study_fk = S.pk
JOIN report_history RH ON RH.report_fk = R.pk
JOIN (
SELECT report_fk, max(revision) AS revision
FROM report_history RH1
GROUP BY 1
) RH1 ON RH1.report_fk = RH.report_fk
AND RH1.revision = RH.revision
WHERE RH.old_status_fk = 21
AND RH.updated_datetime > to_date('22-01-2013', 'DD-MM-YYYY') -- >= ?
AND RH.updated_datetime < to_date('22-01-2014', 'DD-MM-YYYY') -- to_timestamp?
GROUP BY date -- where does date come from?
ORDER BY date;
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