I have made much of what I wanted to work, but there's just one last thing.
=QUERY(ALL!$A$4:$AB, "SELECT A, B, D, C, I, G, O, U, Y, U/I, C/U WHERE A is not null "
&IF(OR(SUFIAN!$F$15="", SUFIAN!$F$16=""), "", " AND C >= "&SUFIAN!F15&" AND C <= "&SUFIAN!F16&"")
&IF(OR(SUFIAN!$H$15="", SUFIAN!$H$16=""), "", " AND G >= "&SUFIAN!H15&" AND G <= "&SUFIAN!H16&"")
&IF(OR(SUFIAN!$G$15="", SUFIAN!$G$16=""), "", " AND I >= "&SUFIAN!G15&" AND I <= "&SUFIAN!G16&"")
&IF(OR(SUFIAN!$I$15="", SUFIAN!$I$16=""), "", " AND O >= "&SUFIAN!I15&" AND O <= "&SUFIAN!I16&"")
&IF(OR(SUFIAN!$J$15="", SUFIAN!$J$16=""), "", " AND U >= "&SUFIAN!J15&" AND U <= "&SUFIAN!J16&"")
&IF(OR(SUFIAN!$K$15="", SUFIAN!$K$16=""), "", " AND Y >= "&SUFIAN!K15&" AND Y <= "&SUFIAN!K16&"")
&IF(OR(SUFIAN!$L$15="", SUFIAN!$L$16=""), "", " AND AA >= "&SUFIAN!L15&" AND AA <= "&SUFIAN!L16&"")
&IF(OR(SUFIAN!$M$15="", SUFIAN!$M$16=""), "", " AND AB >= "&SUFIAN!M15&" AND AB <= "&SUFIAN!M16&""),1)
All of this is working, but when I try to Label the column U/I, and C/U, the query mostly gives me the 'Formula parse error', or sometimes the 'expecting ... instead' error.
I am making a mistake somewhere, probably with the quotations. Let's say I want to name U/I as Orders Per Session, and C/U should be Sales Per Session. Any idea how I can achieve that?