合并两个表并在 PostgreSQL 中计算加权和

Question

我有以下两个table：

表 1

 shopid  hour      category  amount
    ------------------------------------
    1        7          food       10
    1        8          food       15
    1        10         misc.      5
    ...................................

表 2

 shopid  hour      category  amount
    ------------------------------------
    1        7          food       30
    1        8          food       10
    1        9          misc.      10
    ...................................

现在，我想根据他们的 shopid、event_hour 和类别合并两个 table。但是想计算金额上的加权和。条件是，如果我有相同的 shopid、hour、category 那么它将执行加权和。否则，它将保留来自 table1 和 table2 的原始数据。合并后，table 看起来像这样：

合并表

shopid  hour      category  amount
------------------------------------
1        7          food       25   //amount= table1.amount*0.25+ table2.amount*0.75
1        8          food       11.25 //amount= table1.amount*0.25+ table2.amount*0.75
1        9          misc.      10   //this amount remains same as at hour 9 nothing was on table1.
1        10         misc.      5    //this amount remains same as at hour 10 nothing was on table2.
...................................

知道怎么做吗？

Answer 1

嗯。你似乎想要一个 full join 和算术：

select shopid, hour, category,
       (case when t1.shopid is null then t2.amount
             when t2.shopid is null then t1.amount
             else t1.amount * 0.25 + t2.amount * 0.75
        end) as weighted_sum
from table1 t1 full join
     table2 t2
     using (shopid, hour, category)

合并两个表并在 PostgreSQL 中计算加权和

Merging two tables and calculating weighted sum in PostgreSQL

sql

postgresql

union-all