Which two are true about queries using set operators such as UNION? (Choose two.)
Which two are true about queries using set operators such as UNION? (Choose two.)
In a query containing multiple set operators like UNION, several rules apply to how the data types and lengths are handled. CHAR columns of different lengths used with a set operator return a VARCHAR2 whose length equals the longest CHAR value, ensuring data integrity across different sizes (Option D). Additionally, queries using set operators do not perform implicit conversion across different data type groups, which means character, numeric, and other types are kept within their groups without automatic conversion (Option E).
According to: https://docs.oracle.com/cd/B19306_01/server.102/b14200/queries004.htm "If both queries select values of datatype CHAR of equal length, then the returned values have datatype CHAR of that length. If the queries select values of CHAR with different lengths, then the returned value is VARCHAR2 with the length of the larger CHAR value." AND "In queries using set operators, Oracle does not perform implicit conversion across datatype groups. " So DE.
DE are correct
DE are the correct answer
DE are correct
DE are correct
D E are correct. source: https://docs.oracle.com/cd/B19306_01/server.102/b14200/queries004.htm
DE , tested that
Definitely not BC
B is incorrect because it is not mandatory to have an alias for each column in the first SELECT select first_name ||''||last_name, employee_id from hr.employees union select first_name,employee_id from HR.EMPLOYEES order by 1,2; C is incorrect because the datatypes : BLOC,CLOB are not valid the set Operators. DE is the correct answer.
DE are correct
DE are correct
I think it’s BD?
B may be correct if in the end will be "order by" clause. Therefore DE correct