Apr 17, 2026
SQL NULL Handling: COALESCE, NULLIF, and CASE
NULL is not zero and not empty. It means the value is unknown. This post explains how NULL behaves in SQL, how to test for it, and how to handle it safely using COALESCE, NULLIF, and CASE.
Journal
Notes on backend architecture, data engineering, and product-aware system design.
Apr 17, 2026
NULL is not zero and not empty. It means the value is unknown. This post explains how NULL behaves in SQL, how to test for it, and how to handle it safely using COALESCE, NULLIF, and CASE.
Apr 17, 2026
Set operators let you combine the results of two queries into one. This post explains how UNION, UNION ALL, INTERSECT, and EXCEPT work, when to use each one, and how they apply to real data engineering tasks.
Apr 16, 2026
Without an index, every query reads the entire table. This post explains how indexes work, when to create them, how SARGability breaks index usage, and how to read a query plan to confirm performance improvements.
Apr 16, 2026
Window functions let us calculate across related rows without collapsing them like GROUP BY does. This post explains how OVER(), PARTITION BY, ORDER BY, and common window functions work in real data engineering queries.
Showing 1 to 4 of 20 posts