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as previous customers who are no longer active with the company.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
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. The UNION
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
官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e41084/queries004.htm#i2054381