単純なクエリの場合、非常に多くの副選択とWITHステートメントを書き出さなければならないのは気になります。
問題は、サブクエリを持つクエリを単純化する方法に関する基本的なガイドラインはありますか?
これが私の質問です:
WITH cte_min
AS (SELECT a.client_id,
a.specimen_source,
a.received_date
FROM f_accession_daily a
JOIN (SELECT DISTINCT f.client_id,
f.received_date,
f.accession_daily_key
FROM F_ACCESSION_DAILY f
JOIN (SELECT CLIENT_ID,
Min(received_date) MinRecDate
FROM F_ACCESSION_DAILY
GROUP BY CLIENT_ID) i
ON f.CLIENT_ID = i.CLIENT_ID
AND f.RECEIVED_DATE = i.MinRecDate) b
ON a.ACCESSION_DAILY_KEY = b.ACCESSION_DAILY_KEY),
cte_max
AS (SELECT a.client_id,
a.specimen_source,
a.received_date
FROM f_accession_daily a
JOIN (SELECT DISTINCT f.client_id,
f.received_date,
f.accession_daily_key
FROM F_ACCESSION_DAILY f
JOIN (SELECT CLIENT_ID,
Max(received_date) MaxRecDate
FROM F_ACCESSION_DAILY
GROUP BY CLIENT_ID) i
ON f.CLIENT_ID = i.CLIENT_ID
AND f.RECEIVED_DATE = i.MaxRecDate) b
ON a.ACCESSION_DAILY_KEY = b.ACCESSION_DAILY_KEY),
cte_est
AS (SELECT DISTINCT client_id,
MLIS_DATE_ESTABLISHED
FROM D_CLIENT
WHERE REC_ACTIVE_FLG = 1
AND MLIS_DATE_ESTABLISHED IS NOT NULL)
SELECT DISTINCT f.client_id,
cmin.specimen_source,
cmin.received_date,
cmax.specimen_source,
cmax.received_date,
cest.MLIS_DATE_ESTABLISHED
FROM F_ACCESSION_DAILY f
LEFT JOIN cte_max cmax
ON cmax.CLIENT_ID = f.CLIENT_ID
LEFT JOIN cte_min cmin
ON cmin.CLIENT_ID = f.CLIENT_ID
LEFT JOIN cte_est cest
ON cest.CLIENT_ID = f.CLIENT_ID
私は必ずしもあなた自身が単純化することを求めているのではなく(私はこれに非常に感謝しますが)、むしろこのクエリをよりエレガントに書き直すための一般的なガイドライン/指示を求めています。