How to make a query that return data of rows related to each row in table - sql

Question

i have some tables about Double-entry bookkeeping.
table VoucherDetail Contains Accounting Entries for Each Voucher and
other tables are Accounts Group/Ledger/Definitive
here are diagrams of tables
im trying to get opposite side of an entry and show it in a custom column that matches entry debit/credit amount(Ref to image 2).
i did some google search and find nothing. here is the query i made so far(Ref to image 1):
SELECT
dbo.Vouchers.VoucherId,
vd.VoucherDetailIndex AS ind,
vd.Debit,
vd.Credit,
vd.Description,
CONCAT ( ag.Name, '_', al.Name, '_', ad.Name ) AS names,
CONCAT ( ag.GroupId, '_', al.LedgerId, '_', ad.DefinitiveId ) AS ids
FROM dbo.Vouchers
JOIN dbo.VoucherDetails AS vd ON vd.Voucher_VoucherIndex = dbo.Vouchers.VoucherIndex
JOIN dbo.AccDefinitives AS ad ON vd.AccDefinitive_DefinitiveIndex = ad.DefinitiveIndex
JOIN dbo.AccLedgers AS al ON ad.AccLedger_LedgerIndex = al.LedgerIndex
JOIN dbo.AccGroups AS ag ON al.AccGroup_GroupIndex = ag.GroupIndex
here is the result im getting :
result i want to be :
here is an example to explain what i need :
EVENT :
we put 10$ on bank as our Equity, now we need to create a voucher for this:
INSERT INTO Vouchers(VoucherIndex, VoucherId, VoucherDate, Description) VALUES
(1, 1, 2019/01/01, initial investment);
and now we need to add Entry of this event to VoucherDetail of Voucher 1
which will have 2 entry; 1 for cash and 1 for Equity :
INSERT INTO VoucherDetails(VoucherDetailIndex, Debit, Credit, Description AccDefinitive_DefinitiveIndex, AccLedger_LedgerIndex, Voucher_VoucherIndex, EntityOrder) VALUES
(1, 10$, 0, 'Put Cash on Bank as initial Investment', 10101, 101, 1, 1),
(2, 0, 10$, 'initial Investment', 50101, 501, 1, 2);
now we run the first query i provided here is the result
now we have our common result, lets get to the problem
imagine someone filled these tables with 10000 row data
and we need to find Voucher no.10, with 20 entries inside VoucherDetail
we get these entries by doing a simple query.
but we don't know which related to which(like in above example Cash with 10$ debt related to Equity with 10$ credit)
if we want to know it, we need to spend time on it every time we need to find something
the query need to search whole table and find opposite side related to each row based on Debit or Credit value of row
this should be the result i wrote in excel :
as you can see in the image above there is 2 new columns added
Account in opposite Side and Account ID in opposite side
first row refers to Equity which related to Cash and
second row refers to Cash Which related to Equity.

Answer 1

As far as I can see, what you need to be able to do is join two VoucherDetail records that have the same Voucher_VoucherIndex value (let's call this VoucherID for brevity). However, the only two things these records have in common is their VoucherID and the fact that the Debit value = the Credit value in the other, and vice versa.
In the comments you mentioned that multiple VoucherDetail rows with the same VoucherID can have the same Debit value (and I presume Credit value). If this wasn't the case, you could add something like this to your query:
JOIN dbo.VoucherDetails AS vd_opposite
ON vd.Voucher_VoucherIndex = vd_opposite.Voucher_VoucherIndex
AND (vd.Debit = vd_opposite.Credit OR vd.Credit = vd_opposite.Debit)
You can't do this though, because Debit/Credit and VoucherID together are not enough to be unique, so you might pick up extra rows in the join that you don't want.
Therefore, your only option is to add a new ID field to your table (maybe called SaleID or something) that definitively links the two rows that represent opposite sides of the same "sale" with a common ID. Then, the above JOIN would look like this:
JOIN dbo.VoucherDetails AS vd_opposite
ON vd.Voucher_VoucherIndex = vd_opposite.Voucher_VoucherIndex
AND vd.SaleID = vd_opposite.SaleID
In addition to adding that JOIN, you would need to join the new vd_opposite table against all of the dbo.Acc* tables again to get access to the data you want, and obviously add the fields from those tables that you want in the results to your SELECT fields.