ORACLE DATABASE INTERVIEW QUESTIONS

What is the purpose of the UNION operator in SQL?

What is the purpose of the UNION ALL operator in SQL?

Can you use UNION or UNION ALL to combine result sets from different tables with different column names? Provide an example.

How do you ensure the columns in the SELECT statements are compatible when using UNION or UNION ALL?

How do you remove duplicates when using UNION ALL in Oracle?

How do you sort the combined result set when using UNION or UNION ALL in Oracle?

How do you handle NULL values when using UNION and UNION ALL in Oracle?

How do you use UNION or UNION ALL with more complex queries involving joins and subqueries?

How do you optimize performance when using UNION and UNION ALL in Oracle?

Explain a scenario where you need to use both UNION and UNION ALL in a real-world application and how you would implement it in Oracle.