OCP-1Z0-051-V9.02-114题

114. View the Exhibit and examine the structure of the SALES table.

The following query is written to retrieve all those product ID s from the SALES table that have more than 

55000 sold  and have been ordered more than 10 times.

SQL> SELECT prod_id

FROM sales

WHERE quantity_sold > 55000 AND COUNT(*)>10

GROUP BY prod_id

HAVING COUNT(*)>10;

Which statement is true regarding this SQL statement? 

A. It executes successfully and generates the required result.

B. It produces an error because COUNT(*) should be specified in the SELECT clause also.

C. It produces an error because COUNT(*) should be only in the HAVING clause and not in the WHERE

clause.

D. It executes successfully but produces no result because COUNT(prod_id) should be used instead of

COUNT(*).

Answer: C

答案解析：

sh@TEST0924> SELECT prod_id  FROM sales  WHERE quantity_sold > 55000

  2  AND COUNT(*)>10

  3  GROUP BY prod_id

  4  HAVING COUNT(*)>10;

AND COUNT(*)>10

    *

ERROR at line 2:

ORA-00934: group function is not allowed here

 

 因为COUNT(*)只能用在HAVING子句中，不能在WHERE子句中

 where子句不能带组函数