Self-Joins SQL interview questions

Self-joins model hierarchies (who referred whom), pairs (products bought together) and transitions (plan upgrades). Alias carefully and avoid duplicate pairs.

Referrals Within the Same CountrySelf-Joinsmedium
Referral LeaderboardSelf-Joins · Aggregation & GROUP BYmedium
Team to Business UpgradesSelf-Joins · Dates & Timemedium
Frequently Bought TogetherSelf-Joins · Aggregation & GROUP BYhard