Query heterozygous Compound

[LankyAlec]

Good morning, sorry for the trivial question, but I am not able to solve the problem on my own.
on an imported VCF file I would like to run a query to get the variants compatible with a heterozygous compound.
how can I write the clause in the query?

I tried the following query but I got an error.

SELECT ann.gene FROM variants GROUP BY ann.gene HAVING COUNT(ann.gene) >= 2