Read a PostgreSQL query plan without getting lost
Follow the work through a query plan, compare estimates with actual rows, and learn what to investigate before adding another index.
The knowledge library.
Practical answers. Deeper understanding. Find your next database breakthrough.
MySQL composite indexes: why column order matters
Build an index around a real access pattern, then use EXPLAIN to understand what it helps—and what it doesn't.
Window functions: keep the rows, add the context
Calculate a running total and rank orders within each customer without collapsing the underlying rows.
A transaction is a boundary, not a magic shield
Separate atomicity from isolation and learn why two individually correct transactions can still surprise each other.
RDS availability is not a backup strategy
Separate failover, read scaling, and point-in-time recovery before choosing your managed database configuration.
Azure SQL Database or Managed Instance?
Use application dependencies and operating requirements to choose a deployment model, not just a familiar product name.
Cloud SQL connections need a budget
A managed database does not remove connection limits. Coordinate application pools, scaling, and authentication before traffic grows.
SQL joins: a small reference with predictable results
Use a tiny customer-and-order dataset to see inner joins, left joins, and the filter placement that changes their meaning.