Topic
Joins
Combining tables, and knowing which rows you're about to lose. Most join questions here have a LEFT-vs-INNER trap somewhere in them, because that's the mistake that returns a plausible-looking answer instead of an error.
New to this? Read the JOINs: combining tables chapter.
easyOrders with customer namesZalora · joinsFree→easyShow each transaction with its merchant nameBigPay · joinsFree→mediumCustomers who never orderedShopee · joinsBasic→mediumEmployees who out-earn their managerCIMB · joinsBasic→mediumEvery part, with its supplier (if assigned)Toyota · joinsBasic→mediumRevenue per routeAirAsia · joinsBasic→mediumTotal spend per customerMaybank · joinsBasic→hardPair every employee with their managerSime Darby · joinsBasic→hardTotal paid, joined across three tablesMaxis · joinsBasic→hardTotal shipped, joined across three tablesWestern Digital · joinsBasic→