1Z0-051 QUETION 15 别名的用法
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QUESTION 15
View the Exhibit and examine the data in the CUSTOMERS table.
Evaluate the following query:
SQL> SELECT cust_name AS "NAME", cust_credit_limit/2 AS MIDPOINT,MIDPOINT+100 AS "MAX
LOWER LIMIT"
FROM customers;
The above query produces an error on execution.
View the Exhibit and examine the data in the CUSTOMERS table.
Evaluate the following query:
SQL> SELECT cust_name AS "NAME", cust_credit_limit/2 AS MIDPOINT,MIDPOINT+100 AS "MAX
LOWER LIMIT"
FROM customers;
The above query produces an error on execution.
What is the reason for the error?
A. An alias cannot be used in an expression.
B. The a lias NAME should not be enclosed with in double quotation marks .
C. The MIDPOINT+100 expression gives an error because CUST_CREDIT_LIMIT contains NULL values.
D. The a lias MIDPOINT should be enclosed with in double quotation marks for the
CUST_CREDIT_LIMIT/2 expression .
答案:A
解析:
别名不能在SELECT语句中直接使用。
SQL> SELECT cust_name AS "NAME", cust_credit_limit/2 AS MIDPOINT,MIDPOINT+100 AS "MAX 2 LOWER LIMIT" 3 FROM customers; SELECT cust_name AS "NAME", cust_credit_limit/2 AS MIDPOINT,MIDPOINT+100 AS "MAX *ERROR at line 1:ORA-00904: "MIDPOINT": invalid identifier
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