Cascade delete
A foreign key with a cascade delete specifies that if a row in the parent table is deleted, then the corresponding rows in the child tables are automatically deleted.
An infinite delete cascade cycle can occur when table A references table B, table B references table C, table C references table A (and so on) and all delete cascade boxes are checked. While running the delete cascades, if a row is found that was a candidate for deletion during the cycle, an infinite delete cascade cycle occurs and results in a runtime error.