Question

I was wondering which approach is better for designing databases?

I have currently one big table (97 columns per row) with references to lookup tables where I could.

Wouldn’t it be better for performance to group some columns into smaller tables and add them key columns for referencing one whole row?

Answer 1

If you split up your table into several parts, you’ll need additional joins to get all your columns for a single row – that will cost you time.

97 columns isn’t much, really – I’ve seen way beyond 100.

It all depends on how your data is being used – if your row just has 97 columns, all the time, and needs to 97 columns – then it really hardly ever makes sense to split those up into various tables.

It might make sense if:

• you can move some “large” columns (like XML, VARCHAR(MAX) etc.) into a separate table, if you don’t need those all the time -> in that case, your “basic” row becomes smaller and your basic table will perform better – as long as you don’t need those extra large column

• you can move away some columns to a separate table that aren’t always present, e.g. columns that might be “optional” and only present for e.g. 20% of the rows – in that case, you might save yourself some processing for the remaining 80% of the cases where those columns aren’t needed.