International Association of Computer Science and Information Technology(IACSIT)
Parallel DataBase Management Systems (PDBMS) are widely used to process the ever-increasing data volume and complex queries in large-scale enterprise. Business Intelligence (BI) generated a large amount of outer joins to query data warehouses powered by parallel DBMS. With a brief introduction to the development of outer join optimization in parallel DBMS, the authors firstly describe ROJA, DOJA, and DERA three kinds of outer join algorithms, and then compare them with each other which is the main purpose of this paper. At last, they discuss the challenges of outer join optimization that they are currently facing with.