ocp题库解析：1Z0-051-V9.02-第151题
ocp题库解析：1Z0-051-V9.02-第151题，完整题库请点击这里联系老师咨询了解
151. View the Exhibit and examine the structure of the CUSTOMERS and CUST_HISTORY tables.
The CUSTOMERS table contains the current location of all currently active customers. The
CUST_HISTORY table stores historical details relating to any changes in the location of all current as well
as previous customers who are no longer active with the company.
You need to find those customers who have never changed their address.
Which SET operator would you use to get the required output?
A. MINUS
B. UNION
C. INTERSECT
D. UNION ALL
Answer: A
试题解析：
本题意是让找出没有改变过地址的客户。即从CUSTOMERS 减去改变过地址的CUST_HISTORY 的客户即可。
UNION Example The following statement combines the results of two queries with the UNION operator, which eliminates duplicate selected rows. This statement shows that you must match data type (using the TO_CHAR function) when columns do not exist in one or the other table
所有的行都包括
UNION ALL Example The UNION operator returns only distinct rows that appear in either result, while the UNION ALL operator returns all rows. TheUNION ALL operator does not eliminate duplicate selected rows
去除重复的行
INTERSECT Example The following statement combines the results with the INTERSECT operator, which returns only those unique rows returned by both queries
返回共同有的唯一的行
MINUS Example The following statement combines results with the MINUS operator, which returns only unique rows returned by the first query but not by the second
返回第一个有，第二个表无的行
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