OCP-1Z0-051-V9.02-147题

ny3259

　　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 promotions  WHERE 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 promotions  WHERE promo_category='TV')  3  then 'HIGH'  else 'LOW'END COST_REMARK   4  FROM 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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