ORACLE DATABASE INTERVIEW QUESTIONS

What does NULL mean in Oracle?

How do you define a column to be NOT NULL in Oracle?

What happens if you try to insert a NULL value into a NOT NULL column?

How do you add a NOT NULL constraint to an existing column in a table?

Explain how to remove a NOT NULL constraint from a column?

What is the difference between NULL and an empty string in Oracle?

How can you check for NULL values in a query?

What is the purpose of the NVL function, and how is it used?

How does Oracle handle NULL values in aggregate functions?

Explain how to handle NULL values in a complex query using the COALESCE function?