OCP-1Z0-051-V9.02-113题

113. Examine the structure of the ORDERS table:  

Name             Null      Type 

ORDER_ID        NOT NULL    NUMBER(12) 

ORDER_DATE      NOT NULL    TIMESTAMP(6) 

CUSTOMER_ID     NOT NULL    NUMBER(6) 

ORDER_STATUS               NUMBER(2) 

ORDER_TOTAL                NUMBER(8,2)

You want to find the total value of all the orders for each year and issue the following command:

SQL>SELECT TO_CHAR(order_date,'rr'), SUM(order_total)

FROM orders

GROUP BY TO_CHAR(order_date,'yyyy');

Which statement is true regarding the outcome?

A. It executes successfully and gives the correct output.

B. It gives an error because the TO_CHAR function is not valid.

C. It executes successfully but does not give the correct output.

D. It gives an error because the data type conversion in the SELECT list does not match the data type

conversion in the GROUP BY clause. 格式不一致

Answer: D

答案解析：

报错，因为SELECT列表中的数据类型转换与GROUP BY子句中的数据类型转换不匹配。

rr和yyyy的格式不一致，改为一致后可以得出数据。

scott@TEST0924> select to_char(HIREDATE,'rr'),sum(sal)

  2  from emp

  3  group by to_char(HIREDATE,'yyyy');

select to_char(HIREDATE,'rr'),sum(sal)

               *

ERROR at line 1:

ORA-00979: not a GROUP BY expression

 

 

scott@TEST0924>  select to_char(HIREDATE,'yyyy'),sum(sal)

  2  from emp

  3  group by to_char(HIREDATE,'yyyy');

 

TO_C   SUM(SAL)

---- ----------

1987       4100

1980        800

1982       1300

1981      22825

 

scott@TEST0924> select to_char(HIREDATE,'rr'),sum(sal)

  2  from emp

  3  group by to_char(HIREDATE,'rr');

 

TO   SUM(SAL)

-- ----------

87       4100

81      22825

82       1300

80        800