Row countsUNION ALL stacks five counts into one result. Order Details columnspragma_table_info shows the two-column primary key. Territories per employeeFour tables joined through a junction table. Uncovered territoriesLEFT JOIN + IS NULL finds rows with no match. Org chart (recursive)A recursive CTE walks the ReportsTo tree. Price history of Queso CabralesOrder lines keep the price charged on the day. IS NULLThe only reliable test for a missing value. count(*) vs count(column)Why counting after a LEFT JOIN goes wrong. Revenue by categoryGROUP BY with a derived revenue column. Shipper performancejulianday() differences give days to ship. Sales by quarterstrftime() and integer division make quarters. Priciest product per categoryA correlated subquery, run per row. Lost customersEXISTS and NOT EXISTS together. Category Sales for 1997A view built on a view built on a view. + versus ||Why T-SQL string joins return 0 in SQLite. Ten Most Expensive ProductsMicrosoft's procedure, as ORDER BY + LIMIT. Rank within countryrank() OVER (PARTITION BY ...). Running total by monthsum() OVER and lag() for month-on-month. Top two products per categoryrow_number() for a top-N per group. Plan: indexed lookupEXPLAIN QUERY PLAN: SEARCH via an index. Plan: a joinA join that uses a covering index. BLOB sizestypeof() and length() on stored pictures.