Why does my left join in Access have fewer rows than the left table?

Question

I have two tables in an MS Access 2010 database: TBLIndividuals and TblIndividualsUpdates. They have a lot of the same data, but the primary key may not be the same for a gi

Answer 1

ON ( 

        TblIndividuals.FirstName = TblIndividualsUpdates.FirstName

        and 

        TblIndividuals.LastName = TblIndividualsUpdates.LastName

        AND (
                 TblIndividuals.DateBorn = TblIndividualsUpdates.DateBorn      
                 or 
                 (
                     TblIndividuals.DateBorn is null          
                     and 
                     (
                     TblIndividuals.MidName is null 
                     and TblIndividualsUpdates.MidName is null              
                     or TblIndividuals.MidName = TblIndividualsUpdates.MidName
                     )
                 )
             )
    );

What I would do is systematically remove all the join conditions except the first two until you find the records drop off. Then you will know where your problem is.