|My Dear, you have mentioned two table and in each of them you have a Registration number and a registration. Do those two vocabularies mean the same?|
1. if yes, those numbers should not change and should refer to the same and unique person. Meaning in one table registration number should be a primary key and in the other table that same number should exist but as a foreign key in order to link the two tables.
2. if no, then you have to create a foreign key in attendance table in order to link the two table.
when that condition is satisfied, link the two tables and use the condition of GPA>3.0 and Attendance>50%.