Firebird SQL：由於合並而查詢緩慢或者可以重寫

Question

我遇到一些常用查詢的性能問題。

SELECT
v.id,
coalesce((SELECT sum(amount) FROM artjournal WHERE variant_ref=v.id AND storage_ref=1 AND atype_ref in (1,3,4)), 0) "fv", 
coalesce((SELECT sum(amount) FROM artjournal WHERE variant_ref=v.id AND storage_ref=1 AND atype_ref=2), 0) "ivo", 
coalesce((SELECT sum(amount) FROM artjournal WHERE variant_ref=v.id AND storage_ref=1 AND atype_ref=5), 0) "iio", 
coalesce((SELECT sum(amount * mvalue) FROM artjournal WHERE variant_ref=v.id AND storage_ref=1), 0) "vw"
FROM productvariant v

因為artjournal是一張大桌子，每天都有成千上萬的新唱片，演出變得越來越糟糕。

我有所有ID字段的索引。

有沒有辦法重寫這個語句來加快速度？ 或者我可以使用不同的方式從artjournal表中檢索數據，如果結果為null，則返回0？

謝謝你的想法，

克里斯蒂安

Answer 1

看起來你想要一個過濾的聚合：

SELECT v.id,
       sum(case when a.atype_ref in (1,3,4) then a.amount else 0 end) as "fv",
       sum(case when a.atype_ref = 2 then a.amount else 0 end) as "ivo",
       sum(case when a.atype_ref = 5 then a.amount else 0 end) as "iio",
       sum(a.amount * a.mvalue) as "vw"
FROM productvariant v
  LEFT JOIN artjournal a ON a.variant_ref = v.id
WHERE storage_ref = 1
GROUP BY v.id;