SQL cheatsheet

Selects, joins, aggregates, and indexes you will actually type.

Query

Command / topic	What it does
`SELECT a, b FROM t WHERE x = 1;`	Filter rows
`SELECT * FROM t ORDER BY created_at DESC LIMIT 20;`	Latest rows
`SELECT COUNT(*) FROM t GROUP BY status;`	Aggregate by group
`SELECT DISTINCT country FROM users;`	Unique values

Joins

Command / topic	What it does
`INNER JOIN b ON a.id = b.a_id`	Matching rows only
`LEFT JOIN b ON a.id = b.a_id`	Keep left rows even without matches
`EXISTS (SELECT 1 FROM b WHERE …)`	Correlated existence check

Schema helpers

Command / topic	What it does
`CREATE INDEX idx_users_email ON users(email);`	Speed up lookups
`EXPLAIN QUERY PLAN …;`	Inspect how SQLite plans a query
`BEGIN; … COMMIT;`	Wrap changes in a transaction

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