[英]PostgreSQL: Get the second to last MAX(date)
我在PostgreSQL中有兩個視圖。 一個用於獲取每個組織的最新總數。 另一種觀點是獲得每個組織的倒數第二個最新總量,這就是問題:如何在PostgreSQL中獲得倒數第二個MAX(日期)? 這是我的代碼(注意'date'是我的列之一,而不是函數):
CREATE VIEW vw_totaaldossiers AS
SELECT SUM(aantal) as totaal
FROM _dossier i1
WHERE date = (
SELECT MAX(date)
FROM _dossier i2
WHERE i2.instantie = i1.instantie
GROUP BY i2.instantie
);
CREATE VIEW v2_relatiefdossiers AS
SELECT SUM(aantal) as relatief
FROM _dossier i3
WHERE date = (
SELECT /* Here comes the second to last MAX(date) */
FROM _dossier i4
WHERE i4.instantie = i3.instantie
GROUP BY i4.instantie
);
謝謝您的幫助!
SELECT date
FROM _dossier i2
WHERE i2.instantie = i1.instantie
GROUP BY i2.instantie
ORDER BY date DESC LIMIT 1 OFFSET 1
像這樣的東西:
SELECT SUM(aantal) as relatief
FROM _dossier i3
WHERE date = (
SELECT date
from (
select date,
dense_rank() over (partition by i4.instantie order by date desc) as rnk
FROM _dossier i4
WHERE i4.instantie = i3.instantie
) t
where rnk = 2;
);
我不完全確定,i3在嵌套派生表中實際可見!
您需要運行一個explain
來查明Wiktor的LIMI / OFFSET查詢是更快還是更慢。
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