Handy SQL Cheatsheet for developers: covers queries, aggregations, joins, subqueries, and window functions. Searchable and categorized for quick reference. All local processing.
TL;DR: Free online SQL cheat sheet covering queries, aggregations, joins, subqueries, window functions, and date handling, with runnable examples. Keyword search and category browsing. Runs locally.
This tool runs entirely in your browser. Open DevTools → Network panel and search your input — it appears in no request.
Usage Guide
SQL cheatsheet: SELECT / JOIN / aggregation / subquery / window functions — syntax and examples sorted by frequency. Local static page, no network lookup. Built for quick syntax reference while writing queries, interview prep, or as a team handbook.
1. How to use
- Find the syntax by category (basic queries / multi-table joins / aggregations).
- Read the example, copy, swap in your table and column names.
- Pair with the sql-formatter tool to prettify long queries before reading.
2. Frequent scenarios
- Multi-table joins: INNER JOIN for intersection, LEFT JOIN to keep all left rows — do not confuse them.
- Grouped stats: GROUP BY + COUNT/SUM/AVG, filter groups with HAVING.
- Deduplication: DISTINCT or GROUP BY — the latter is more flexible but slightly slower.
3. A performance note
Applying functions to columns in WHERE (e.g. WHERE YEAR(create_time)=2026) kills the index — rewrite as a range (WHERE create_time BETWEEN ...). Same for LIKE '%xxx%' with a leading wildcard. Run EXPLAIN to see the execution plan; type=ALL means full table scan and must be optimized.
4. Reading execution plans before blaming the query
Most slow queries are not slow because of syntax but because of what the engine does with it. Run EXPLAIN before your SELECT and read two fields first: type (ALL means a full table scan — usually the problem) and rows (how many rows the engine expects to touch). An index that looks present but unused is the classic trap: functions on columns in WHERE, LIKE with a leading wildcard, and mismatched column types between JOIN tables all silently disable indexes. Fix the shape of the predicate rather than adding more indexes — each extra index taxes every INSERT and UPDATE.
FAQ
Completely free with no registration. Syntax references load locally for offline browsing anytime.
Common syntax for queries, aggregations, joins, subqueries, window functions, and date handling, each with examples.
Yes. Keyword search and category browsing let you filter by syntax name or function quickly.
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