Dev
Mock Postgres Query Generator
SQL fluency comes from reading and tweaking real queries, not from memorising syntax. When you need a realistic query to test a database tool, practice against, or paste into documentation, writing one from scratch means looking up the correct JOIN syntax, GROUP BY rules, and PostgreSQL date functions every time. This tool generates a valid PostgreSQL SELECT query from a pool of four patterns. There are no inputs — each click produces one of: a LEFT JOIN counting orders per user filtered to the last 30 days with GROUP BY and ORDER BY; a simple products SELECT with a price filter; a JOIN on orders and users filtering by status; or a monthly revenue rollup using date_trunc('month', created_at) with SUM and GROUP BY. All queries end with a semicolon and use idiomatic PostgreSQL syntax. Copy the output into a psql console to see it execute (if your schema matches), adapt it to your own table and column names, or use it as a test fixture for a query builder or ORM. Reading varied, working queries and understanding why each clause is there builds SQL intuition faster than any tutorial.
How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Click Generate to produce a SQL query.
- Copy it into a console or test.
- Adapt the table and column names.
- Run it after tailoring to your schema.
Use Cases
- •Learning SQL queries
- •Demoing query patterns
- •Documenting a database schema
- •Testing a query tool
- •Practising joins and aggregates
Tips
- →LEFT JOIN keeps unmatched left rows.
- →GROUP BY enables aggregates.
- →Adapt names to your schema.
- →Read and tweak to build fluency.
FAQ
what query patterns does the generator produce
One of four patterns at random: a LEFT JOIN counting orders per user (last 30 days, GROUP BY, ORDER BY, LIMIT 10); a filtered products SELECT by price and stock; an INNER JOIN on orders and users filtered by status; or a monthly revenue rollup using date_trunc and SUM. Each click picks one at random.
what is the difference between join and left join
An INNER JOIN (or plain JOIN) returns only rows that have a match in both tables. A LEFT JOIN returns all rows from the left table, with NULLs in the right-table columns where there is no match. In the orders-per-user query, a LEFT JOIN ensures users with no orders still appear in the result with a count of zero.
what does date_trunc do in the monthly revenue query
date_trunc('month', created_at) truncates a timestamp to the start of its month — so '2025-06-22 14:30' becomes '2025-06-01 00:00:00'. Using it in GROUP BY groups all rows from the same month together, enabling a monthly aggregate like SUM(total). It is idiomatic PostgreSQL for time-series reporting.
can I run these queries against my database
Only after adapting them. The queries use generic table and column names (users, orders, products, price, in_stock) that are unlikely to match your schema exactly. Adapt the table names, column names, and filter values to your real schema before running. The SQL is valid standard PostgreSQL syntax — only the schema-specific names need updating.
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