Postgres vs MySQL vs SQLite: Comparing SQL Performance Across Engines

🗄️ Which SQL engine is best for your needs? PostgreSQL, MySQL, and SQLite have key differences in syntax and performance.

What differentiates them in practice:

Date arithmetic:

PostgreSQL: end_date - start_date directly → returns days (elegant and clean)
MySQL: requires DATEDIFF(end_date, start_date) (explicit function call)
SQLite: uses julianday() to convert to numbers + CAST to simulate CEILING()

CTEs and Window Functions:

PostgreSQL and MySQL 8.0+ support them efficiently
MySQL < 8.0 required subqueries
SQLite supports them from version 3.25+

Indexing:

PostgreSQL → excels with composite indexes for GROUP BY
MySQL (InnoDB) → automatically clusters data by primary key
SQLite → indexes on JOIN columns improve performance for local queries

When to use each:

SQLite: prototypes, mobile apps, small serverless datasets
MySQL: high-concurrency web apps, LAMP ecosystem
PostgreSQL: complex analytics, native JSON, geospatial operations

💡 Explanation in a nutshell
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The difference between the three engines isn’t just raw performance — it’s SQL ergonomics: PostgreSQL offers the most expressive syntax, MySQL the best balance for traditional web apps, and SQLite unmatched portability. Knowing their syntax differences prevents surprises when migrating queries between engines.