Question

我的当前表格如下

public.transactions

storeId     FeatureA  FeatureB  FeatureC  Details
123         true      false     false     ... (JSON)
123         false     false     false
123         true      false     true

基本上，交易表会跟踪触发交易的特定功能。我需要获取特定ID的每个功能的数量，例如：

storeId     FeatureA  FeatureB  FeatureC
123         2         0         1

我已经进行了3次独立计数

Select *
FROM public.transactions
where "storeId" = 123 AND "FeatureA" = true

但是似乎效率很低。

Answer 1

您是否只需要条件聚合？ Postgres通过支持filter子句使此操作变得容易：

select storeid,
       count(*) filter (where featureA) as num_featureA,
       count(*) filter (where featureB) as num_featureB,
       count(*) filter (where featureC) as num_featureC
from public.transactions t
group by storeid;

Answer 2

有条件聚合：

select storeid,
  sum(case when featurea then 1 else 0 end) featurea,
  sum(case when featureb then 1 else 0 end) featureb,
  sum(case when featurec then 1 else 0 end) featurec
from tablename
group by storeid

依靠多个布尔列

2 个答案: