Observed arrival · 2026-10-18
QueryCrack’s MySQL row-read challenges
QueryCrack offers MySQL 8 challenges for practicing indexes and query plans, grading queries by how many rows the storage engine actually reads.
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- For
- MySQL learners practicing indexes and query plans
- Worth noticing
- A logically correct query can receive TIME_LIMIT if it exceeds a challenge’s row-read budget.
Field notes
Each challenge supplies a fixed schema and index set, then measures session-status Handler_read_* deltas in MySQL 8.0. The grading threshold is actual storage-engine rows touched, not elapsed time or the optimizer’s estimate; exceeding the challenge’s row budget can return TIME_LIMIT even when the query is logically correct. The homepage lists warm-up, core, and boss exercises, including ranking, reporting, and latest-record queries.
Observed signals
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