Nested Loop Join

Nested Loop Join is a fundamental join algorithm used in database query processing to combine rows from two tables based on a join condition. It works by iterating through each row in the outer table and, for each row, scanning all rows in the inner table to find matches. This algorithm is simple to implement but can be inefficient for large datasets due to its quadratic time complexity.

Also known as: Nested Loop, Nested-Loop Join, Nested Loop Algorithm, NLJ, Nested Iteration

Why learn Nested Loop Join?

Developers should learn Nested Loop Join when working with database systems, query optimization, or building data processing applications, as it's a core concept in SQL execution. It's particularly useful for small tables, ad-hoc queries, or when no indexes are available, but should be avoided for large-scale joins where more efficient algorithms like Hash Join or Merge Join are preferred.

Learning Resources

• docs: PostgreSQL Documentation: Nested Loop Joins
• tutorial: GeeksforGeeks: Nested Loop Join in DBMS
• video: YouTube: Database Joins Explained (Nested Loop, Hash, Merge)
• course: Coursera: Database Management Essentials