filter data multiple dropdown google sheets

Question

I am trying to filter data from my google sheed with multiple dropdowns my spredsheet looks like this:

I have 2 tabs. tab 1 has all by info and tab 2 is where i am trying to filter data. I would like to have dropdowns above age, book 1 and book 2 to filter these options but when i do this it will not disply all eg. if i only want to find people who have finished book 1 i dont want to apply a filter to the other dropdowns.

=query(tab1!A:D, " select * where B = '"&B2&"' AND C = '"&C2&"' " AND D = '"&D2&"' "  )

Answer 1

= looks whether it is exactly equal. Since B2/C2/D2 is blank, it'll filter all conditions and then provide the filtered data. You might wanna use matches or contains.

  =QUERY(tab1!A:D, " select * where B contains '"&B2&"' AND C contains '"&C2&"' AND D contains '"&D2&"' "  )

There was also an extra " in your formula.