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Editorial Team
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Asked: 2026-05-31T16:42:09+00:00

I have to load the data shown in the below image into my database.

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I have to load the data shown in the below image into my database.

For a particular row, either field PartID would be NULL OR field GroupID will be NULL, and the other available columns refers to the NON-NULL entity. I have following three options:

  1. To use one database table, which will have one unified column say ID, which will have PartID and GroupID data. But, in this case I won’t be able to apply foreign key constraint, as this column will be containing both entities’ data.
  2. To use one database table, which will have columns for both PartID and GroupID, which will contain the respective data. For each row, one of them will be NULL, But in this case I will be able to apply foreign key constraint.
  3. To use two database tables, which will have similar structure, the only difference will be the column PartID and GroupID. In this case I will be able to apply foreign key constraint.

One thing to note here is that, the table(s) will be used in import processes to import about 30000 rows in one go and will also be heavily used in data retrieve operations. Also, the other columns will be used as pivot columns.

Can someone please suggest what should be best approach to achieve this?

enter image description here

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1 Answer

  1. Editorial Team

    I would use option 2 and add a constraint that only one can be non-null and the other must be null (just to be safe). I would not use option 1 because of the lack of a FK and the possibility of linking to the wrong table when not obeying the type identifier in the join.

    There is a 4th option, which is to normalize them as “items” with another (surrogate) key and two link tables which link items to either parts or groups. This eliminates NULLs. There are further problems with that approach (items might be in both again or neither without any simple constraint), so unless that is necessary for other reasons, I wouldn’t generally go down that path.

    Option 3 could be fine – it really depends if these rows are a relation – i.e. data associated with a primary key. That’s one huge problem I see with the data presented, the lack of a candidate key – I think you need to address that first.

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