Strategies for checking ISNULL on varbinary fields?

Question

In the past I\'ve noted terrible performance when querying a varbinary(max) column. Understandable, but it also seems to happen when checking if it\'s null or not, and I was

Answer 1

I think it's slow because the varbinary column is not (and can't be) indexed. Therefore, your approach to use a computed (and indexed) column is valid.

However, I would use ISNULL(DATALENGTH(Content), -1) instead, so that you can distinguish between length 0 and NULL. Or just use DATALENGTH(Content). I mean, Microsoft SQL Server is not Oracle where an empty string is the same as NULL.

Answer 2

We had a similar problem when looking for rows where a varbinary value was not null. For us the solution was to update the statistics for the database:

exec sp_updatestats

After doing this the queries ran much faster.