what's best way to leave empty database cells?

Question

I'm not that experienced with databases. If I have a database table containing a lot of empty cells, what's the best way to leave them (e.g. so performance isn't degraded, memory is not consumed, if this is even possible)?

I know there's a "null" value. Is there a "none" value or equivalent that has no drawbacks? Or by just not filling the cell, it's considered empty, so there's nothing left to do? Sorry if it's silly question. Sometimes you don't know what you don't know...

Not trying to get into a discussion of normalizing the database. Just wondering what the conventional wisdom is for blank/empty/none cells.

Thanks

Answer 1

The convention is to use null to signify a missing value. That's the purpose of null in SQL.

Noted database researcher C. J. Date writes frequently about his objections to the handling of null in SQL at a logical level, and he would say any column that may be missing belongs in a separate table, so that the absence of a row corresponds to a missing value.

I'm not aware of any serious efficiency drawbacks of using null. Efficiency of any features depend on the specific database implementation you use. You haven't said if you use MySQL, Oracle, Microsoft SQL Server, or other.

MySQL's InnoDB storage engine, for example, doesn't store nulls among the columns of a row, it just stores the non-null columns. Other databases may do this differently. Likewise nulls in indexes should be handled efficiently, but it varies from product to product.