Naming Category and SubCategory Tables - sql

Question

I'm trying to create a bunch of lookup tables in a database but am stuck when it comes to naming them. The tables are like this:
1. dbo.AccountType (this is the highest level category)
2. dbo.AccountSubType (this is a 2nd level category)
3. dbo.AccountSubSubType (this is a 3rd level category)
The above naming convention breaks easily. So perhaps this is better:
1. dbo.AccountType1 (highest level)
2. dbo.AccountType2 (second level)
3. dbo.AccountType3 (third level)
4. dbo.AccountType-N (and so on...)
I know naming conventions are opinion based, but surely there has to be some logical way to do this that is scalable and not confusing to developers.
Example of how the data looks in the dbo.AccountType2 table using the second solution:
AccountTypeID (FK) | AccountType1ID (FK) | AccountType2ID (PK) | AccountType2
=============================================================================
1 4 1 Credit Card
1 5 2 Savings
Is there any better way to store hierarchical data in a database and name the tables correctly?

Answer 1

This would probably be better represented as a single table with a hierarchical relationship:
E.g.
CREATE TABLE [dbo].[AccountType] (
Id int NOT NULL
,ParentId int NULL
CONSTRAINT [FK_AccountType_AccountType_Parent] REFERENCES [dbo].[AccountType] (Id)
,Name nvarchar(200) NOT NULL
CONSTRAINT [PK_AccountType] PRIMARY KEY CLUSTERED ([Id])
)
Then populate it with data as follows:
INSERT INTO dbo.AccountType (Id, ParentId, Name) VALUES (1, NULL, 'Credit Card')
INSERT INTO dbo.AccountType (Id, ParentId, Name) VALUES (2, 1, 'Credit Card Sub-Type')
INSERT INTO dbo.AccountType (Id, ParentId, Name) VALUES (3, 2, 'Credit Card Sub-Sub-Type')
INSERT INTO dbo.AccountType (Id, ParentId, Name) VALUES (4, NULL, 'Savings')
INSERT INTO dbo.AccountType (Id, ParentId, Name) VALUES (5, 4, 'Savingsd Sub-Type')
INSERT INTO dbo.AccountType (Id, ParentId, Name) VALUES (6, 5, 'Savings Sub-Sub-Type')
Anything with a ParentId of NULL is a root value, otherwise it is a child of the specified parent...
Edit: To query you'd use a CTE. E.g.
WITH ParentAccountType ( Id, ParentId, Name, ParentName )
AS
(
SELECT Id, ParentId, Name, CAST('N/A' AS nvarchar(200)) AS ParentName
FROM AccountType
WHERE ParentId IS NULL
UNION ALL
SELECT c.Id, c.ParentId, c.Name, p.Name AS ParentName
FROM
AccountType c
INNER JOIN ParentAccountType p ON c.ParentId = p.Id
)
SELECT ParentName, Name
FROM ParentAccountType
GO
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