19.choose the best answer

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 promo category 'TV' .

B) It produces an error because subqueries cannot be used with the CASE expression.

C) It shows COST_REMARK for all the promos in the table.

D) It produces an error because the subquery gives an error.

Answer：C

(解析：category 'TV'只是判定 promo_cost 的一个条件，显示的是所有 category 的内容。

使用如下语句验证：

SELECT promo_name,promo_category,CASE

WHEN promo_cost>=(SELECT AVG(promo_cost)

FROM promotions

WHERE promo_category= 'TV')

THEN 'HIGH'

ELSE 'LOW'

END COST_REMARK

FROM promotions

where rownum < 30;

)