47.View the Exhibit and examine the structure of ORD and ORD_ITEMS tables.

47.View the Exhibit and examine the structure of ORD and ORD_ITEMS tables.

The ORD_NO column is PRIMARY KEY in the ORD table and the ORD_NO and ITEM_NO columns are

composite PRIMARY KEY in the ORD_ITEMS table.

Which two CREATE INDEX statements are valid? (Choose two.)

A.CREATE INDEX ord_idx1 ON ord(ord_no);

B.CREATE INDEX ord_idx2 ON ord_items(ord_no);

C.CREATE INDEX ord_idx3 ON ord_items(item_no);

D.CREATE INDEX ord_idx4 ON ord,ord_items(ord_no, ord_date,qty);

答案：BC

解析：主键会自动创建索引

ORD表ord_no为主键，那么ord_no会创建索引

ORD_ITEMS表ORD_NO和ITEM_NO为联合主键，那么ORD_NO和ITEM_NO会创建联合索引

索引不能重复，因此A，错误，D错误