"Get or create" is a very common operation for syncing data in the database, but implementing it correctly may be trickier than you may expect. If you ever had to implement it in a real system with real-life load, you may have overlooked potential race conditions, concurrency issues and even bloat!

PostgreSQL zero-downtime migrations made easy

A lightweight message queue. Like AWS SQS and RSMQ but on Postgres.

Subqueries and performance in PostgreSQL

Mini ORM for Python, with support for Postgres, MySQL, SQLite to be used with async frameworks

A truly Open Source MongoDB alternative, built on Postgres

The (composite_value).* expansion to columns was new to me. And useful in a recent query I had to write.

Free multi-platform database tool for developers, SQL programmers, database administrators and analysts. Supports all popular databases: MySQL, PostgreSQL, MariaDB, SQLite, Oracle, DB2, SQL Server, Sybase, MS Access, Teradata, Firebird, Derby, etc.