The image cncpt155.gif shows a parent table and its child table. Rows 1 through 4 of the parent table are indexed on keys 1 through 4, respectively. The child table is not foreign-key indexed to the parent table. Row 3 in the parent table is updated and acquires an exclusive row lock. At the same time, the child table acquires a share lock on the whole table.
End of image description.