SQL guides

Every query in these guides runs on the practice bakery database.

• SQL interview questions, with answers you can runThe SQL questions that come up most in interviews: second highest, duplicates, top per group, joins, WHERE vs HAVING. Each has a query tested on a practice database.
• SQL joins explained, with one example of eachHow INNER, LEFT, RIGHT, FULL, CROSS and self joins differ, which rows each keeps, and when to use them, with examples on a practice database.
• SQL cheat sheet (PostgreSQL)A short SQL cheat sheet: SELECT, WHERE, GROUP BY, JOIN, CASE, window functions, CTEs and changing data. Every example is tested on a practice database.
• SQL dialect differences: what changes between databasesWhere PostgreSQL, MySQL, SQL Server, SQLite and Oracle differ: limiting rows, joining text, dates, auto-numbering and division. The core of SQL stays the same.