Question

我试图找到特定年份的total service costs（想想牙医可能会做的程序）。我有一个service表，其中包含serviceID and serviceCost。在visit表中，我有date, visitID, and patientID（我想从这张表中提取日期，因为其他人没有理由从中提取日期）。另一个能够completedservice，所以我有serviceID and visitID（如果访问ID是2000，并且有人完成了多项服务，它将使用不同的serviceID多次列出2000次。）

我想我明白我需要做什么，但是我被抛弃了。任何帮助表示赞赏。

这是我到目前为止所做的：

Select s.serviceID, Count(s.serviceID)*s.serviceCost
From completedservice cs, service s, visit v
Where
  cs.serviceID = s.serviceID
  AND cs.visitID = v.visitID
  AND visitDate BETWEEN '2007-01-01' AND '2007-12-31'
Group By s.serviceID;

completedService表：

completedServiceID, serviceID, visitID
1   1   1
2   2   1

服务表：

serviceID, serviceCost
1            20
2            20

访问表格

visitID    visitDate
1           2007-08-10
2           2007-08-12

感谢您帮助我将所有内容拼凑在一起的指导。

Answer 1

您需要将访问次数乘以每项服务的服务费用：

SELECT
    SUM(tbl.total_cost) AS total
FROM
(
SELECT 
    s.serviceID, 
    COUNT(s.serviceID)*s.serviceCost AS total_cost
FROM 
    completedservice cs, service s, visit v
WHERE
    cs.serviceID = s.serviceID 
AND 
    cs.visitID = v.visitID 
AND 
    visitDate BETWEEN '2007-01-01' AND '2007-12-31'
GROUP BY
    s.serviceID
) AS tbl;

这假设服务成本在期间不会改变。如果更改，则需要为每个时段执行此过程。

http://sqlfiddle.com/#!9/9605e/5

Answer 2

Select SUM(s.serviceCost)
From visit v
  Join completedservice cs on cs.visitID = v.visitID
    Join service s on s.serviceID = cs.serviceID
Where v.visitDate BETWEEN '2007-01-01' AND '2007-12-31'

此查询逐行执行：

Calculate total sum spent
during all visits
by finding all completed services on each visit
and finding details of each service (that was completed)
where visit date is in 2007

跨3个表的聚合列

2 个答案: