Top 85 PostgreSQL Interview Questions & Answers (2026)

01 What is PostgreSQL? 02 What is the difference between PostgreSQL and MySQL? 03 What is a database in PostgreSQL? 04 What is a schema in PostgreSQL? 05 How do you connect to PostgreSQL using psql? 06 What are the basic data types in PostgreSQL? 07 How do you create a table in PostgreSQL? 08 How do you insert data into a PostgreSQL table? 09 How do you query data in PostgreSQL? 10 What is a PRIMARY KEY in PostgreSQL? 11 What is a FOREIGN KEY in PostgreSQL? 12 What is the difference between WHERE and HAVING? 13 What are aggregate functions in PostgreSQL? 14 How do you use GROUP BY in PostgreSQL? 15 How do you sort query results in PostgreSQL? 16 What are JOINs in PostgreSQL? 17 What is the difference between INNER JOIN and LEFT JOIN? 18 How do you update records in PostgreSQL? 19 How do you delete records in PostgreSQL? 20 What is the LIMIT and OFFSET clause in PostgreSQL? 21 What is a VIEW in PostgreSQL? 22 What is a sequence in PostgreSQL? 23 What is the difference between CHAR, VARCHAR, and TEXT in PostgreSQL? 24 What is a NULL value in PostgreSQL? 25 How do you use LIKE and ILIKE in PostgreSQL? 26 What are constraints in PostgreSQL? 27 How do you add or drop a column from a table? 28 What is TRUNCATE and how does it differ from DELETE? 29 What is the RETURNING clause in PostgreSQL? 30 What is a transaction in PostgreSQL? 31 What are indexes in PostgreSQL? 32 How do you create an index in PostgreSQL? 33 What is EXPLAIN in PostgreSQL? 34 How do you use DISTINCT in PostgreSQL? 35 What is the difference between UNION and UNION ALL? 36 What is a subquery in PostgreSQL? 37 How do you use COALESCE in PostgreSQL? 38 What are some common string functions in PostgreSQL? 39 What are common date/time functions in PostgreSQL? 40 What is the difference between NOW() and CURRENT_TIMESTAMP in PostgreSQL? 41 How do you use CASE expressions in PostgreSQL? 42 How do you create a user and grant privileges in PostgreSQL?

01 What are CTEs (Common Table Expressions) in PostgreSQL? 02 What are window functions in PostgreSQL? 03 What are partial indexes in PostgreSQL? 04 What are expression indexes in PostgreSQL? 05 What is MVCC in PostgreSQL? 06 What are isolation levels in PostgreSQL? 07 What is the difference between VACUUM and ANALYZE in PostgreSQL? 08 What is autovacuum in PostgreSQL? 09 What is a materialized view in PostgreSQL? 10 How does JSONB differ from JSON in PostgreSQL? 11 How do you index JSONB columns in PostgreSQL? 12 What is the ON CONFLICT clause (upsert) in PostgreSQL? 13 What are triggers in PostgreSQL? 14 What are stored procedures and functions in PostgreSQL? 15 What is the pg_stat_activity view? 16 How do you find and kill long-running queries in PostgreSQL? 17 What are table inheritance and partitioning in PostgreSQL? 18 How do you use ARRAY data type in PostgreSQL? 19 What is the hstore extension in PostgreSQL? 20 What are advisory locks in PostgreSQL? 21 How does connection pooling work with PostgreSQL? 22 What is WAL (Write-Ahead Logging) in PostgreSQL? 23 What is streaming replication in PostgreSQL? 24 What are the differences between a B-tree, GIN, GiST, and BRIN index? 25 How do you use full-text search in PostgreSQL? 26 What are generated columns in PostgreSQL?

01 What is the query planner in PostgreSQL and how does it work? 02 What causes poor query plans and how do you fix them? 03 What is logical replication in PostgreSQL? 04 How do you implement row-level security (RLS) in PostgreSQL? 05 What is table bloat in PostgreSQL and how do you fix it? 06 How does PostgreSQL handle deadlocks? 07 What are advisory locks vs regular locks in PostgreSQL? 08 How do you implement partitioned tables efficiently in PostgreSQL? 09 What is pg_cron and how do you schedule jobs in PostgreSQL? 10 How do you use EXPLAIN ANALYZE effectively in PostgreSQL? 11 What is the difference between LATERAL joins and correlated subqueries? 12 What is pg_partman and how does it simplify partition management? 13 How do you perform zero-downtime schema migrations in PostgreSQL? 14 What are exclusion constraints in PostgreSQL? 15 How do you use pg_dump and pg_restore for backup and restore? 16 What is connection pooling with PgBouncer and when should you use it? 17 How do you monitor PostgreSQL performance in production?