Which of the following SQL queries counts the number of occurrences for each value of the field order_type in the table orders?
A.
SELECT order_type,COUNT(*) FROM orders WHERE order_type=order_type;
B.
SELECT order_type,COUNT(*) FROM orders GROUP BY order_type;
C.
COUNT(SELECT order_type FROM orders);
D.
SELECT COUNT(*) FROM orders ORDER BY order_type;
E.
SELECT AUTO_COUNT FROM orders COUNT order_type;
題解
SELECT敘述可以使用GROUP BY關鍵字來合併重複的欄位，答案是選項B。