SQL for developers is how you read and write the systems you already ship — user accounts, orders, feature flags, observability tables. Backend engineers, full-stack builders, and data engineers share the same primitives: relational tables , stable keys , honest JOIN semantics around NULL , explicit grain for aggregates, and ACID discipline when concurrency hits. What follows mirrors how teams onboard ICs — schema literacy, guarded CRUD, predicate hygiene, joins without silent row multiplication, GROUP BY / HAVING versus window analytics, then indexes , transactions , and EXPLAIN as your debugging lingua franca — every numbered skill block ends like sql interview questions with answers : runnable Postgres SQL, traced execution, and a terse why . After the hero art, dive straight into reps when you crave keyboard time: Browse practice hub → , open SQL practice → , deepen joins → , reinforce filters → , or widen with database fundamentals → .…