SQL Debit and Credit tables - sql

Question

I got a database project from my university to finish, but I am stack at the structure of debit and credit table that how to make it in SQL Server, my code is shown here:
create table AcCat
(
CatID smallint Primary Key,
CatName nvarchar(20)
)
Create Table Accounts
(
AcID int Primary key,
AcNumber int,
AcName nvarchar(20),
AcCategory smallint references AcCat(CatID)
)
Create Table Transactions
(
TrnRef bigint primary key identity (1,1),
TrnDate datetime
)
Create Table Voucher
(
VID bigint primary key identity (1,1),
TranRef bigint references Transactions(TrnRef),
AccountNo int references Accounts(AcID),
DrCr nvarchar(2),
Amount money,
Narration nvarchar(100)
)
Create Table Voucher_2
(
V2ID bigint primary key identity (1,1),
V2TranRef bigint references Transactions(TrnRef),
V2DebitAc int references Accounts(AcID),
V2CreditAc int references Accounts(AcID),
Amount money,
Narration nvarchar(100)
)
I don't know above table structure are correct or not, but I am stuck at the Voucher and Voucher_2 tables that which one I should use for my Database.
The tables output is following
My tables Output

Answer 1

Either one seems serviceable. Are you given example queries that should be run over your system? If so, have you tried writing those queries and seeing whether one or other of your structures makes all of those queries harder or simpler? Also, have you considered what integrity constraints you may wish the database to enforce?
For instance, finding the current balance of an account can be reasonably performed using either structure.:
SELECT
ac.AcNumber,
SUM(CASE WHEN DrCr = 'Cr' THEN Amount
ELSE -Amount END) as Balance
FROM
Accounts ac
inner join
Voucher v
on
ac.AcID = v.AccountNo
WHERE
ac.AcNumber = 1010
GROUP BY
ac.AcNumber
SELECT
ac.AcNumber,
SUM(CASE WHEN V2DebitAc = V2CreditAc THEN 0
WHEN V2CreditAc = ac.AciD THEN Amount
ELSE -Amount END) as Balance
FROM
Accounts ac
inner join
Voucher_2 v
on
ac.AcID = v.V2DebitAc or
ac.AcID = v.V2CreditAc
WHERE
ac.AcNumber = 1010
GROUP BY
ac.AcNumber
If all transactions are required to be balanced, how will you ensure that there are always pairs of rows in Voucher that match each other?
If you have to apply interest of other account corrections, what account will you match those with in Voucher_2?
If you haven't been given any scenarios to work against, try to conjure some up like the above and see how well they fit. Without further information though, I'd say either will probably work.
One thing I'd serious recommend fixing though - having all of AcNumber, AccountNum and AcID seems like a recipe for confusion. I'd probably just use AcID everywhere outside of the Accounts table unless you want to go one step further and just use AcNumber as a natural key and use it everywhere and remove AcID from the picture. Certainly I didn't expect (before writing the queries) that I'd find AccountNum also in the picture and it's not the same thing as AcNumber.
Where possible I'd advise using as few names as possible. Ideally, everywhere in your schema that you encounter a particular column name, it should mean the same concept, and you shouldn't encounter the same concept under any other names.