Why SQL UNIQUE Constraints Allow Duplicate NULLs
Quick Answer: In SQL, unique constraints permit multiple NULL values because NULL represents an unknown state rather than an empty value, meaning two NULLs are never equal (NULL = NULL evaluates to UN
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SQL NOT IN vs NOT EXISTS: Handling NULL Values Safely
Quick Answer: In SQL, using WHERE column NOT IN (SELECT ...) returns zero rows if the subquery contains a single NULL. This occurs because NOT IN expands to chained != operators joined by AND, and any
Preventing Lost Update Race Conditions with Atomic SQL
TL;DR: When multiple requests read and update the same database record simultaneously, performing calculations in your application code causes race conditions and lost updates. To prevent this, delega
When to Use an ORM vs SQL and Query Builders
ORMs like Prisma and Hibernate are excellent for simplifying basic CRUD operations. However, for complex queries involving window functions, CTEs, or deep joins, ORMs often get in the way. For advance
Solving the N+1 Query Problem in Databases and ORMs
TL;DR: The N+1 query problem occurs when an ORM executes one initial database query followed by N subsequent queries to fetch related child data. I solve this by using SQL joins, batch fetching (IN qu
How Database Reads Work: Pages, Buffer Pools, and Disk
Quick Answer: When you query a database, it rarely reads a single row directly from disk. Instead, it relies on RAM. Databases load fixed-size blocks of data called "pages" (typically 8KB) into a memo
