Short Answer
Learn standard SQL once — it transfers 90%. Then pick PostgreSQL for analytics depth (better window functions, CTEs, JSONB, extensions like pgvector for AI). MySQL dominates legacy app backends and is asked in service-company interviews.
Feature Table
| Feature | MySQL 8 | PostgreSQL 15+ |
|---|---|---|
| Window functions | ✅ | ✅ richer |
| CTEs (incl. recursive) | ✅ | ✅ + materialised |
| JSON | JSON type | JSONB (faster, indexed) |
| Arrays/custom types | ❌ | ✅ |
| Full-text search | Basic | Strong (tsvector) |
| AI/vector (pgvector) | ❌ | ✅ |
Interview Advice
Say: "I work in PostgreSQL; syntax transfers to MySQL." Then prove JOINs + windows + one CTE live. Practice: SQL playground.
Verdict by Profile
- Student (0 experience): pick the easier-start option first; depth later.
- Working professional: pick what automates your current job fastest.
- Job switcher: pick what interviews test most (SQL + the other tool).
60-Day Learning Order (Both)
Days 1–30: master tool A basics + 20 problems. Days 31–45: tool B basics. Days 46–60: one combined project using both — that project is your interview story.
14-Day MySQL → PostgreSQL Switch
- Days 1–5: install Postgres; re-run your 20 core queries — note ARRAY_AGG, FILTER (WHERE...), RETURNING differences.
- Days 6–10: JSONB operators (->, ->>, @>) + one GIN index demo.
- Days 11–14: pgvector hello-world: embed 500 rows, similarity search — instant RAG talking point.
Frequently Asked Questions
- Which DB do companies use most?
Mixed: MySQL in apps, Postgres in analytics/startups, warehouses (Snowflake/BigQuery) on top. - Should freshers learn both?
Master standard SQL on one; mention the other. - Postgres for AI?
Yes — pgvector makes it the default for RAG demos.
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