Question

I have a script where a user can select a field across multiple tables. It uses a Union to get all of the rows. Right now, I have a mapping array to indicate whether a specific field exists in each table, and if it doesn’t, it uses "" as field_name to keep everything in check.

I was wondering if there is a way to reference a possibly non-existent column in a query, something like COALESCE so that if the column doesn’t exist, instead of throwing an error, it just returns a default value.

Answer 1

coalesce would still require a fieldname, so it wouldn’t help:

... COALESCE(non_existent_field, NULL)

will still cause an error due to the field not existing.