OCP-1Z0-051-V9.02-148題
148. View the Exhibit and examine the structure of the PRODUCTS tables.
You want to generate a report that displays the average list price of product categories where the average
list price is less than half the maximum in each category.
Which query would give the correct output?
A. SELECT prod_category,avg(prod_list_price)
FROM products
GROUP BY prod_category
HAVING avg(prod_list_price) < ALL 小於所有，小於最小值
(SELECT max(prod_list_price)/2
FROM products
GROUP BY prod_category);
B. SELECT prod_category,avg(prod_list_price)
FROM products
GROUP BY prod_category
HAVING avg(prod_list_price) > ANY
(SELECT max(prod_list_price)/2
FROM products GROUP BY prod_category);C. SELECT prod_category,avg(prod_list_price)
FROM products
HAVING avg(prod_list_price) < ALL
(SELECT max(prod_list_price)/2
FROM products
GROUP BY prod_category);
D. SELECT prod_category,avg(prod_list_price)
FROM products
GROUP BY prod_category
HAVING avg(prod_list_price) > ANY
(SELECT max(prod_list_price)/2
FROM products);
Answer: A
答案解析：
1、首先查詢子查詢中出每個PROD_CATEGORY的prod_list_price的最大值的1/2的值。
[email protected]> SELECT max(prod_list_price)/2 FROM products 2 GROUP BY prod_category; MAX(PROD_LIST_PRICE)/2 ---------------------- 99.995 649.995 299.995 549.995 499.995 2、找出prod_list_price的平均值 [email protected]> SELECT prod_category,avg(prod_list_price) 2 FROM products 3 GROUP BY prod_category; PROD_CATEGORY AVG(PROD_LIST_PRICE) -------------------------------------------------- -------------------- Software/Other 31.4130769 Hardware 1149.99 Electronics 121.682308 Photo 230.19 Peripherals and Accessories 145.085238 3、平均值小於1/2最大值的所有值 ，即小於最小值 [email protected]> SELECT prod_category,avg(prod_list_price) FROM products GROUP BY prod_category 2 having avg(prod_list_price)<all(SELECT max(prod_list_price)/2 FROM products GROUP BY prod_category); PROD_CATEGORY AVG(PROD_LIST_PRICE) -------------------------------------------------- -------------------- Software/Other 31.4130769 故選A答案。 B與題意不符，> ANY大於最小值 [email protected]> SELECT prod_category,avg(prod_list_price) 2 FROM products 3 GROUP BY prod_category 4 HAVING avg(prod_list_price) > ANY 5 (SELECT max(prod_list_price)/2 6 FROM products 7 GROUP BY prod_category); PROD_CATEGORY AVG(PROD_LIST_PRICE) -------------------------------------------------- -------------------- Hardware 1149.99 Electronics 121.682308 Photo 230.19 Peripherals and Accessories 145.085238 C語法錯誤，缺少group by [email protected]> SELECT prod_category,avg(prod_list_price) 2 FROM products 3 HAVING avg(prod_list_price) < ALL 4 (SELECT max(prod_list_price)/2 5 FROM products 6 GROUP BY prod_category); SELECT prod_category,avg(prod_list_price) * ERROR at line 1: ORA-00937: not a single-group group function D與題意不符，沒有in each category分組。 [email protected]> SELECT max(prod_list_price)/2 FROM products; MAX(PROD_LIST_PRICE)/2 ---------------------- 649.995 [email protected]> SELECT prod_category,avg(prod_list_price) 2 FROM products 3 GROUP BY prod_category 4 HAVING avg(prod_list_price) > ANY 5 (SELECT max(prod_list_price)/2 6 FROM products); PROD_CATEGORY AVG(PROD_LIST_PRICE) -------------------------------------------------- -------------------- Hardware 1149.99