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Asked: 2026-05-27T20:21:35+00:00

Problem statement – [Business] 1—* [Branch] A business must have one or more branch(es).

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Problem statement – [Business] 1—* [Branch] A business must have one or more branch(es). Only one branch can be main branch.

I am have two design in my mind

  1. [Branch table] – {id, BusinessID (FK), Name, etc , IsMainBranch}
  2. [Branch table] – {id, BusinessID (FK), Name, etc }, [MainBranch table] – {BranchID (PK, FK), BusinessID (FK)}.
  3. [Business table] – {id, name, mainbranchid}, [Branch table] – {id, BusinessID (FK), Name, etc}

Problem with #1 – To put constrain on IsMainBranch I have to use triggers, which can go out of sync latter.

Problem with #2 – Bit complicated to access the data in EF.

Problem with #3 – Don’t think its a good design.

I am using EF 4.1 as ORM and don’t want to make things complicated, which design I should choose. Please suggest if there is a better/alternate way available for the same.

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1 Answer

  1. Editorial Team

    With SQL Server 2008+ you can use filtered indexes

    In your Branch table, just have a flag IsMainBranch. Then create a unique filtered index: this will allow one row only where IsMainBranch= 1 per Business.

    Branch table:

    id (PK)
BusinessID (FK)
Name
...
IsMainBranch

    Then

    CREATE UNIQUE INDEX IX_MainBranch 
        ON Branch(BusinessID) 
        WHERE IsMainBranch = 1;

    This gives

    • simpler table structure
    • no triggers
    • the DB engine enforces this for you
    • no circular FKs (no MainBranchID in the Business table)

    Also see:

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