5 Data
Every entry filed under Data and its subtopics.
What kind of help
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
6 entries match these filters
- 0238 Redis persistence and high availability: RDB, AOF, replicas and Sentinel Redis keeps data in memory and writes it to disk with RDB snapshots, an append-only file, or both. Replicas copy data to… Intermediate · Explains an idea · Linux Article Administration & persistence 15 Oct 2026
- 0216 MySQL vs MariaDB: what actually differs MariaDB started as a fork of MySQL and still speaks the same client protocol, but GTIDs, JSON storage, authentication and tooling have… Intermediate · Explains an idea · Linux Article Choosing a database · MySQL & MariaDB 15 Oct 2026
- 0201 pg_hba.conf and PostgreSQL authentication methods pg_hba.conf decides who may connect from where and how they must prove who they are. Rules are checked top to bottom and… Intermediate · Explains an idea · Linux Article Install & connect · Security & access 15 Oct 2026
- 0204 VACUUM, autovacuum and table bloat in PostgreSQL Updates and deletes leave dead row versions behind. VACUUM makes that space reusable, keeps statistics fresh and prevents transaction ID wraparound; autovacuum… Intermediate · Explains an idea · Linux Article Performance & tuning · Roles & administration 15 Oct 2026
- 0068 SQL joins explained: INNER, LEFT and finding rows with no match A join combines rows from two tables using a matching condition. INNER JOIN keeps only matches, LEFT JOIN keeps every row from… Intermediate · Explains an idea · Any system Article Joins 15 Oct 2026
- 0069 NULL in SQL: why = NULL never matches and how to handle missing values NULL means "unknown", so comparisons with it are neither true nor false. Use IS NULL, COALESCE and careful aggregates to avoid rows… Intermediate · Explains an idea · Any system Article Queries 15 Oct 2026