On the performance of one-to-many data transformations.
Paulo Carreira, Héléna Galhardas, João Pereira, Fernando Martins, Mário J. Silva · 2007
Relational Database Systems often support activities like data warehousing, cleaning and integration. All these activ-ities require performing some sort of data transformations. Since data often resides on relational databases, data trans-formations are often specified using SQL, which is based on relational algebra. However, many useful data transforma-tions cannot be expressed as SQL queries due to the lim-ited expressive power of relational algebra. In particular, an important class of data transformations that produces several output tuples for a single input tuple cannot be ex-pressed in that way. In this paper, we analyze alternatives to process one-to-many data transformations using Relational Database Management Systems, and compare them in terms of expressiveness, optimizability and performance. 1.