Unknown column l.zipcode in field list

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SQL

This is the code but why is there an error of Unknown column l.zipcode in field list when i declare location at the beginning?

select l.zipcode,sum(dum.tab) from location l,
(select count( Pickup_location) as tab from booking b,location l where b.pickup_location = l.Zip_Code
union select count(destination) as tab from booking_destinations bd inner join location l on bd.destination = l.Zip_Code where bd.sequence in(1,2,3)
union select count(destination) as tab from booking_destinations bd,location l where bd.destination = l.Zip_Code and sequence = 4
) as dum where l.zipcode = 18953;

What I have tried:

i have tried removing location at the beginning of sql statement