Sql learning progress Solutions to challenges on W3Schools SQL-Academy SQL-Bolt PostgreSQL Exercises HackerRank Codecademy Codewars SQL-EX Frequently used functions Aggregate Avg Count Max Min Sum Conversion Cast Convert Date & Time Datediff Datepart Expressions Case Coalesce Top Limit Distinct Mathematical Ceiling Floor Sqrt Power Ranking Row_number Rank String Concat Len Left Ltrim Lower Replace Right Substring