I tried this:

from Table where (:par1 is null or col1 = :par1)

but it happens that

from Table where :par1 is null

always returns all the rows of the table, even if the :par1 is not null.

while

 select * from table where col1 = 'asdf'

does not return any row.

I can't use native grammars because my application is supposed to run on different database engines

hibernate hql
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