I feel so stupid right now!!!

@LeFlawk customer table is the parent table to borrow and it has 7 rows...I'm trying to insert 8th row in borrow table while the parent table only has 7 rows...

In order to get this work..I need to have 8 rows in customer table...

So I need to have n rows in customer table in order have n rows in borrow table

Or you could just borrow from the same customer as before. It's not 1-1 relationship, but instead 1-m. But without a context, borrowing from a customer seems wierd. What kind of service is this? Bank?

@joas exactly