Home » Oracle » 1z0-051 » Which statement is true regarding the UNION operator?
Which statement is true regarding the UNION operator?
A. The number of columns selected in all SELECT statements need to be the same
B. Names of all columns must be identical across all SELECT statements
C. By default, the output is not sorted
D. NULL values are not ignored during duplicate checking
Correct Answer: A
Explanation/Reference:
Explanation:
The SQL UNION query allows you to combine the result sets of two or more SQL SELECT statements. It removes duplicate rows between the various SELECT statements.
Each SQL SELECT statement within the UNION query must have the same number of fields in the result sets with similar data types.
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I think C is the only correct answer here.
Nope, D is correct.
God damn, A & D are correct!
AD correct answers
NULLs are not ignored during duplicate checking. Fact check below
select NULL , 1 from dual
UNION
select NULL, 1 from dual;
AD correct