View the Exhibit and examine the structure of ORD and ORD_ITEMS tables.
In the ORD table, the PRIMARY KEY is ORD_NO and in the ORD_ITEMS tables the composite PRIMARY KEY is (ORD_NO, ITEM_NO).
Which two CREATE INDEX statements are valid? (Choose two.)
A.
CREATE INDEX ord_idx
ON ord(ord_no);
B.
CREATE INDEX ord_idx
ON ord_items(ord_no);
C.
CREATE INDEX ord_idx
ON ord_items(item_no);
D.
CREATE INDEX ord_idx
ON ord,ord_items(ord_no, ord_date,qty);
Why is Option A not valid? There is nothing wrong with the syntax. Any logical reason why not A?
There is nothing wrong with the syntax.
But the ORD table has already the ORD_NO primary key.