SQL - Join multiple table - sql

Question

I have four tables Customer, Sales, Invoice, and Receipt.
Customer
ID Name
1 A
Sales
ID Name
1 Ben
Invoice
ID Amt Date CustomerID SalesID
1 12 1/9/2014 1 1
2 10 1/10/2014 1 1
3 20 2/10/2014 1 1
4 30 3/10/2014 1 1
Receipt
ID Amt Date CustomerID SalesID
1 10 4/10/2014 1 1
I wish to join those 4 table as below with sum up the Ammount(s), but I am stuck as to how I can achieve my desired
RESULT
CustomerID SalesID Inv_Amt Rep_Amt Month
1 1 12 0 9
1 1 60 10 10
I've been stuck for days. But, I have no idea how to proceed.

Answer 1

You can get month wise total receipt and invoice amount by grouping and sub query like below :
SELECT Invoice.CustomerID [CustomerID],
Invoice.SalesID [SalesID],
SUM(Invoice.Amt) [Invoice_Amt],
ISNULL((SELECT SUM(Amt)
FROM Receipt
WHERE CustomerID = Invoice.CustomerID
AND SalesID = Invoice.SalesID
AND Month(Date) = Month(Invoice.Date)),0) [Receipt_Amt],
MONTH(Invoice.Date) Month
FROM Invoice
GROUP BY Invoice.CustomerID, Invoice.SalesID, MONTH(Invoice.Date)
SQL Fiddle Demo1
Warning : Here data will come for all months which are in Invoice table. If for any month, there is no any data in invoice table then no result will come for that month even for receipt also.
UPDATE:
To get result from all months of invoice and receipt table, you need to get it using CTE as like below :
;with CTE as
(
SELECT Invoice.CustomerID, Invoice.SalesID, MONTH(Invoice.Date) MonthNo FROM Invoice
UNION
SELECT Receipt.CustomerID, Receipt.SalesID, MONTH(Receipt.Date) MonthNo FROM Receipt
)
SELECT CTE.CustomerID [CustomerID],
CTE.SalesID [SalesID],
ISNULL((SELECT SUM(Amt)
FROM Invoice
WHERE CustomerID = CTE.CustomerID
AND SalesID = CTE.SalesID
AND Month(Date) = CTE.MonthNo),0) [Invoice_Amt],
ISNULL((SELECT SUM(Amt)
FROM Receipt
WHERE CustomerID = CTE.CustomerID
AND SalesID = CTE.SalesID
AND Month(Date) = CTE.MonthNo),0) [Receipt_Amt],
MonthNo
FROM CTE
SQL Fiddle Demo2

Answer 2

Frankly, since you're just selecting customer and sales IDs (as opposed to names), you don't even need to joint all four tables:
SELECT i.CustomerID,
i.SalesID,
SUM(i.Amt) AS InvAmt,
SUM(r.Amt) AS RepAmt,
MONTH(i.`Date`) AS `Month`
FROM Invoice i
JOIN Receipt r ON i.CustomerID = r.CustomerID AND
i.SalesID = r.SalesID AND
MONTH(i.`Date`) = MONTH(r.`Date`)
GROUP BY i.CustomerID, i.SalesID, MONTH(i.`Date`) AS `Month`

Answer 3

Looks like a homework, but ...
SELECT
Customer.ID AS CustomerID,
Sales.ID AS SalesID,
Invoice.Amt AS Inv_Amt,
Receipt.Amt AS Rep_Amt,
MONTH(Invoice.Date) AS Month
FROM
Customer
INNER JOIN Receipt ON Customer.ID = Receipt.CustomerID
INNER JOIN Invoice ON Customer.ID = Invoice.CustomerID
INNER JOIN Sales ON Sales.ID = Receipt.SalesID
I didn't bother checking the result is what you expect, but the query should be something like that. You can play with the join conditions in order to get the result.