David Hayes

Sort-merge joins work in a similar way to hash joins in that each table is accessed independently. This time instead of using a hash the two rowsets are sorted on the join key. Once both rowsets are sorted they are merged on the join key using a merge join algorithm.

Sort-merge joins have the same advantages as hash joins but are far less robust since both rowsets need to be loaded into memory and sorted before the join can occur. You should only use this join method if a hash join is not available (Oracle databases using the Rules Based Optiomiser)

Uncategorized /Databases