SQL中的SUM函数

Question

有三个表，我们必须使用一个主键和外键从这些表中选择数据。但是在一个表中，第三个表中有很多数据。我们必须在主键的基础上总结数据。

BAl = Balance, met = Method, amo = amount, cst_id, cut_id, cut_i = customer_id 

现在，我们要总结的方法和总和在同一查询10卡斯特ID的基础上。谁可以帮我这个事？

Answer 1

如果您提供一些示例数据，编写查询将更容易帮助您。 但是，如果你的MET字段是数字，你想总结它，那么你需要。

select 
    t1.cst_n, t2.bal, 
    sum(t3.met) as met, 
    sum(t3.amo) as amo 
from table1 as t1 
    inner join table2 as t2 on t2.cut_id = t1.cst_id 
    inner join table3 as t3 on t3.cut_i = t1.cst_id 
group by t1.cst_n, t2.bal 

好，如果你想要为所有10个客户数据总结成一个数字，可能你只需要

select 
    sum(t3.met) as met, 
    sum(t3.amo) as amo 
from table3 as t3 
where t3.cut_i in (select t.customerid from @<your variable table with cust. ids> as t) 

Answer 2

;WITH cte 
AS 
(
    SELECT 
     *, 
     ROW_NUMBER() OVER (ORDER BY t1.cst_id) RowNum 
    FROM Table1 t1 
    INNER JOIN Table2 t2 
      ON t1.cst_id = t2.cut_id 
    INNER JOIN Table3 t3 
      ON t2.cut_id = t3.customer_id 
      AND t2.BAL = t3.Balance 
      AND t2.amo = t3.amount 
) 
SELECT SUM(*) 
FROM cte 
WHERE RowNum Between 1 AND 10 
-- You can add a GROUP BY here