Cascade, NO ACTION, Restrict, set NULL in MySQL foreign key settings

First, Cascade Way
Synchronize update/delete out a matching record of a child table when Update/delete records on the parent table

Second, SET NULL mode
Set the column of the matching record on the child table to NULL when the record is update/delete on the parent table
Note that the foreign key column of the child table cannot be not NULL

Third, No action mode
If there are matching records in the child table, the Update/delete action is not allowed for the parent table corresponding to the candidate key

Four, restrict way
Same no action, check foreign KEY constraints immediately

Five, Set default mode
When a parent table has a change, the child table sets the foreign key column to a default value but InnoDB does not recognize

Cascade, NO ACTION, Restrict, set NULL in MySQL foreign key settings