Totally agree with both of you. I’ve been in data engineering roles where selecting the right join literally made or broke reports. So, let’s talk real-world scenarios — when to use which one.
Use INNER JOIN when you only want rows that match on both sides.
- Choose LEFT JOIN when the left table holds your ‘main’ data and you just want to check for related info on the right.
- Go with RIGHT JOIN when the right table is more important in the context (which is less common, honestly).
- If you’re looking to merge everything regardless of matches, that’s a FULL JOIN job.
- And CROSS JOIN — that’s mostly academic unless you’re doing all possible combinations for analysis.
So ultimately, understanding left join vs right join helps you frame your data — it’s about what data matters most and what gaps you’re okay with.