OCP-1Z0-051-V9.02-52题

52. View the Exhibit and examine the structure of the PRODUCTS table.
Using the PRODUCTS table, you issue the following query to generate the names, current list price,
and discounted list price for all those products whose list price falls below $10 after a discount of 25% is
applied on it.
SQL>SELECT prod_name, prod_list_price,
prod_list_price - (prod_list_price * .25) "DISCOUNTED_PRICE"
FROM products
WHERE discounted_price < 10;
The query generates an error.
What is the reason for the error?



A. The parenthesis should be added to enclose the entire expression.
B. The double quotation marks should be removed from the column alias.
C. The column alias should be replaced with the expression in the WHERE clause.
D. The column alias should be put in uppercase and enclosed with in double quotation marks in the
WHERE clause.
Answer: C
答案解析：

where子句不能跟别名,可以跟表达式
实验验证：

scott@TESTDB> select empno,ename,sal+10 "sal10" from emp where sal10<1500;
select empno,ename,sal+10 "sal10" from emp where sal10<1500
*
ERROR at line 1:
ORA-00904: "SAL10": invalid identifier


scott@TESTDB> select empno,ename,sal+10 "sal10" from emp where sal+10<1500;

EMPNO ENAME sal10
---------- ---------- ----------
7369 SMITH 810
7521 WARD 1260
7654 MARTIN 1260
7876 ADAMS 1110
7900 JAMES 960
7934 MILLER 1310

6 rows selected.