第 77 题 (多选题)： Which four statements are true regarding primary and foreign key constraints and the effect they can have on table data.

A. It is possible for child rows that have a foreign key to remain in the child table at the time the parent row is deleted. B. Primary key and foreign key constraints can be defined at both the column and table level. C. A table can have only one primary key and one foreign key. D. A table can have only one primary key but multiple foreign keys . E. Only the primary key can be defined at the column and table level. F. The foreign key columns and parent table primary key columns must have the same names. G. It is possible for child rows that have a foreign key to be deleted automatically from the child table at the time the parent row is deleted 显示答案