SQL / MySQL

1SELECT, WHERE & ORDER BYRetrieve, filter, sort and page through rows, and understand how MySQL really executes a query.7 min 2Aggregations & GROUP BYSummarise data with COUNT, SUM and AVG, group by one or more columns, and filter groups with HAVING.7 min 3JOINsCombine rows from several tables with INNER, LEFT and self joins, and avoid the classic double-counting traps.7 min 4Subqueries & CTEsNest queries inside queries and break complex logic into readable steps with WITH clauses.7 min 5Window functionsRank, running totals and period-over-period comparisons without collapsing rows.7 min 6Creating tables & indexes in MySQLDesign schemas with the right column types, keys, constraints and indexes, and alter them safely.8 min 7INSERT, UPDATE, DELETE & transactionsChange data safely, use upserts and group changes into all-or-nothing transactions.7 min 8Query performance with EXPLAINRead execution plans, design composite indexes and rewrite slow queries.7 min