A tiny mistake in SQL that can change everything.

If the business asks you: "Pull all sales from the Manchester branch in May and July 2024.”

Do you think the query below returns the correct result?

Answer: No. Here’s why

SQL evaluates AND before OR. That means the query is actually read as:

This will include any order placed before July 1st, 2024, even if it’s not from the Manchester branch.

To fix this, we need to group our conditions properly with parentheses:

It is important to always be careful with AND/OR precedence in SQL, as it can completely change your results.