Which two are true about a SQL statement using SET operators such as UNION? (Choose two.)
A. The data type group of each column returned by the second query must match the data type of the corresponding column returned by the first query.
B. The number, but not names, of columns must be identical for all SELECT statements in the query.
C. The data type of each column returned by the second query must exactly match the data type of the corresponding column returned by the first query.
D. The names and number of columns must be identical for all SELECT statements in the query.
E. The data type of each column returned by the second query must be implicitly convertible to the data type of the corresponding column returned by the first query.
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A, B
AB
A is correct
For SET operator, Data type group should be matched.
B- correct
select id from s1 — number
union
select transaction_id from transactions — varchar2
select * from s1
*
ERROR at line 1:
ORA-01790: expression must have same datatype as corresponding expression
AB