Data LiteracyData Literacy

SQLiteracy · skill review

Your SQL skills

Every exercise trains named skills, and this page keeps score: a skill counts as mastered when you've passed every exercise that teaches it. Progress syncs to your account and follows you to any device.

select-basicsSELECT, FROM, and choosing columns0 of 4 passed
limitingLIMIT and working with big tables safely0 of 3 passed
aliasingRenaming columns with AS0 of 1 passed
distinctDeduplicating values with DISTINCT0 of 5 passed
countingCOUNT(*) and COUNT(column)0 of 10 passed
filteringWHERE with comparison operators0 of 12 passed
logical-operatorsCombining conditions with AND, OR, and NOT0 of 3 passed
pattern-matchingLIKE and wildcard patterns0 of 1 passed
set-membershipIN lists and BETWEEN ranges0 of 3 passed
sortingORDER BY, ASC/DESC, and multi-key sorts0 of 14 passed
top-nORDER BY with LIMIT for top-N questions0 of 9 passed
schema-readingReading a schema panel and table structures0 of 1 passed
null-filteringRecognizing and handling NULLs in filters and aggregates0 of 13 passed
aggregationAggregate functions, GROUP BY, and HAVING0 of 29 passed
joinsCombining tables with JOIN and table aliases0 of 11 passed
derived-tablesSubqueries in FROM and staged query building0 of 6 passed
window-functionsOVER, PARTITION BY, ranking, and LAG/LEAD0 of 7 passed
trend-analysisMonth-over-month, year-over-year, and moving averages0 of 4 passed
conditional-logicCASE expressions, NULLIF, and guarded division0 of 6 passed
outer-joinsLEFT JOIN and NULL-extended rows0 of 6 passed
anti-joinsFinding missing rows with LEFT JOIN ... IS NULL and NOT EXISTS0 of 6 passed
set-operationsUNION, INTERSECT, and EXCEPT0 of 5 passed
ctesWITH clauses and readable multi-stage queries0 of 10 passed
grain-awarenessRow grain, weighted averages, and honest ratios0 of 6 passed