Join types directly affect which rows appear in a result set, so choosing the wrong one can silently remove data or introduce NULL values. This is especially important in reporting and reconciliation work done in platforms such as Infosys Cobalt data solutions.
Explain the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN in PostgreSQL. You should describe what rows each join returns, how unmatched rows are represented, and when you would choose one join type over another.
Keep your answer practical and interview-focused. The interviewer is typically looking for clear definitions, simple examples, and an explanation of how NULL values appear in unmatched rows. It is also helpful to mention that RIGHT JOIN is often logically equivalent to swapping table order in a LEFT JOIN.
Join types directly affect which rows appear in a result set, so choosing the wrong one can silently remove data or introduce NULL values. This is especially important in reporting and reconciliation work done in platforms such as Infosys Cobalt data solutions.
Explain the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN in PostgreSQL. You should describe what rows each join returns, how unmatched rows are represented, and when you would choose one join type over another.
Keep your answer practical and interview-focused. The interviewer is typically looking for clear definitions, simple examples, and an explanation of how NULL values appear in unmatched rows. It is also helpful to mention that RIGHT JOIN is often logically equivalent to swapping table order in a LEFT JOIN.
