Merge Join
Merge Join is a database query execution algorithm used to combine two sorted input datasets based on a join condition, typically equality. It operates by scanning both inputs simultaneously in sorted order, matching rows where the join keys are equal, and is highly efficient for large datasets when inputs are pre-sorted or can be sorted cheaply. This algorithm is a fundamental component of relational database management systems (RDBMS) for performing JOIN operations in SQL queries.
Developers should learn Merge Join when optimizing SQL queries in database systems, as it is crucial for understanding query performance, especially for large-scale data processing where sorted inputs reduce I/O and computational overhead. It is particularly useful in scenarios involving equi-joins on indexed or sorted columns, such as in data warehousing, analytics, and applications requiring efficient joins between large tables, helping to avoid costly full table scans.