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BytePatterns

SQL

Queries you can watch run — joins, groups, indexes, transactions.

SQL progress0 / 15
  1. SELECT BasicsName the columns you want; the table hands them back.4m
  2. WHERE and FilteringFilter in the database, not in your application loop.4m
  3. ORDER BY and LIMITSort once in the engine, then take only the slice you show.4m
  4. Aggregations & GROUP BYFold many rows into one number per group.5m
  5. INNER and OUTER JOINsMatch rows across tables — and decide who survives a miss.6m
  6. SubqueriesA query inside a query, answered before the outer one runs.5m
  7. IndexesA second, sorted copy of one column that ends the full scan.6m
  8. Transactions & ACIDAll of the writes land, or none of them do.6m
  9. Query Execution OrderSQL is written top-down but evaluated in a different order.5m
  10. The N+1 Query ProblemOne query for the list, then one more for every single row.5m
  11. Window FunctionsAggregate across rows without collapsing them.6m
  12. CTEs and RecursionName a result, then build the next one on top of it.6m
  13. Composite IndexesColumn order decides which queries the index can serve.6m
  14. Isolation LevelsHow much of another transaction's mess you are allowed to see.6m
  15. Reading a Query PlanStop guessing why it is slow — ask the engine what it did.6m

Quiz yourself: 3 questions from this module

1 / 3

What does SELECT actually describe?