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PostgreSQL
The world’s most advanced open source database. SQL fluency, indexes, and transaction isolation are must-knows.
Topics
SQL Fundamentals
SELECT, GROUP BY, HAVING, subqueries, and CTEs.
Joins
INNER, LEFT, RIGHT, FULL OUTER joins with examples.
Indexes
B-tree, Hash, GIN, EXPLAIN ANALYZE, and index design.
Transactions
ACID properties, isolation levels, and deadlocks.
◆ ACID Properties
Atomicity — all or nothing. Consistency — data stays valid. Isolation — transactions don’t interfere. Durability — committed data survives crashes.
💡 Interview Tip
Practice writing window functions (
ROW_NUMBER, RANK, LAG, LEAD) — they’re a common senior-level SQL interview topic that trips up many candidates.