Using Online Analytical Processing (OLAP) in Data Warehousing

Data warehousing is needed in recent time to give information, that helps in the development of a company, support decision makers, it provides an efficient ways for transforming, manipulating analyzing large amount of data from different organizations or companies. In this paper we aimed to over view, data warehousing definition, how data are gathered from multi sources in to data warehousing using a model. Important techniques were shown, how to analyze data using data warehousing, to make decisions, this technique called Online Analytical Processing OLAP.