OCP-1Z0-051-V9.02-163题

163. View the Exhibit and examine the description for the CUSTOMERS table.

You want  to update  the CUST_CREDIT_LIMIT column  to NULL for all  the customers, where

CUST_INCOME_LEVEL has NULL in the CUSTOMERS table. Which SQL statement will accomplish the

task?

 

A. UPDATE customers

SET cust_credit_limit = NULL

WHERE CUST_INCOME_LEVEL = NULL; 

B. UPDATE customers

SET cust_credit_limit = NULL

WHERE cust_income_level IS NULL;

C. UPDATE customers

SET cust_credit_limit = TO_NUMBER(NULL)

WHERE cust_income_level = TO_NUMBER(NULL);

D. UPDATE customers

SET cust_credit_limit = TO_NUMBER(' ',9999)

WHERE cust_income_level IS NULL;

Answer: B

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12885143

题意要求：更新CUSTOMERS表中所有customers的CUST_CREDIT_LIMIT值，当CUST_INCOME_LEVEL为NULL时更新CUST_CREDIT_LIMIT为空。

AC的where条件都为假，所有都不更新。

D的set语句有语法问题，故错误。

 实验验证：

A,

sh@TESTDB> UPDATE customers

  2  SET cust_credit_limit = NULL

  3  WHERE CUST_INCOME_LEVEL = NULL;

 

0 rows updated.

 B,

sh@TESTDB> UPDATE customers

  2  SET cust_credit_limit = NULL

  3  WHERE cust_income_level IS NULL

  4  ;

 

41 rows updated.

 

 C,

sh@TESTDB> UPDATE customers

  2  SET cust_credit_limit = TO_NUMBER(NULL)

  3  WHERE cust_income_level = TO_NUMBER(NULL);

 

0 rows updated.

 

 D,

sh@TESTDB> UPDATE customers

  2  SET cust_credit_limit = TO_NUMBER(' ',9999)

  3  WHERE cust_income_level IS NULL;

SET cust_credit_limit = TO_NUMBER(' ',9999)

                                  *

ERROR at line 2:

ORA-01722: invalid number