Merge Join Showplan Operator
The Merge Join operator performs the inner join, left outer join, left semi join, left anti semi join, right outer join, right semi join, right anti semi join, and union logical operations.
In the Argument column, the Merge Join operator contains a MERGE:() predicate if the operation is performing a one-to-many join, or a MANY-TO-MANY MERGE:() predicate if the operation is performing a many-to-many join. The Argument column also includes a comma-separated list of columns used to perform the operation. The Merge Join operator requires two inputs sorted on their respective columns, possibly by inserting explicit sort operations into the query plan. Merge join is particularly effective if explicit sorting is not required, for example, if there is a suitable B-tree index in the database or if the sort order can be exploited for multiple operations, such as a merge join and grouping with roll up.
Merge Join is a physical operator.
Graphical execution plan icon
TasksHow to: Display an Actual Execution Plan
ConceptsLogical and Physical Operators Reference
Understanding Merge Joins
Using Inner Joins
Displaying Execution Plans by Using the Showplan SET Options (Transact-SQL)