OCP-1Z0-051-V9.02-147题
147. View the Exhibit and examine the structure of the PROMOTIONS table.Evaluate the following SQL statement:
SQL>SELECT promo_name,CASE
WHEN promo_cost >=(SELECT AVG(promo_cost)
FROM promotions
WHERE promo_category='TV')
then 'HIGH'
else 'LOW'
END COST_REMARK
FROM promotions;
Which statement is true regarding the outcome of the above query?
A. It shows COST_REMARK for all the promos in the table. 分类显示所有值
B. It produces an error because the subquery gives an error.
C. It shows COST_REMARK for all the promos in the promo category 'TV'.
D. It produces an error because subqueries cannot be used with the CASE expression.
Answer: A
答案解析：
1、首先运行子查询，得出一个数值
sh@TEST0910> SELECT AVG(promo_cost) FROM promotionsWHERE promo_category='TV';AVG(PROMO_COST)--------------- 46260.8696 2、所有的promos 根据上面计算的数值，来进行分类。故选择A
sh@TEST0910> SELECT promo_name,CASE WHEN promo_cost >=2(SELECT AVG(promo_cost) FROM promotionsWHERE promo_category='TV')3then 'HIGH'else 'LOW'END COST_REMARK 4FROM promotions;PROMO_NAME COST------------------------------ ----NO PROMOTION # LOWnewspaper promotion #16-108 LOWpost promotion #20-232 LOWnewspaper promotion #16-349 LOWinternet promotion #14-471 LOW
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