In the era of the internet, the sources of data collection are drastically increasing. It becomes a challenge to many organisations to manage these huge volume databases. All organisations collect the data from various resources very easily. The representation of data collected from various resources is not in similar format. It may be possible that all parameters of collected data are not useful for organization. An organisation may find few attributes from some sources useful for them and some from other sources. They have to combine all required field from the different dataset into one dataset. They analyse this dataset as per their requirement and take decision related to their business. In any business only extraction of data is not sufficient they want the analysis of the data also. Knowledge extracted from operational databases is frequently required by the top officials or executives to make better decisions. An aggregation is one kind of knowledge computed by processing one or more selected attributes of the database table and is useful to perform analysis. Decision support and information retrieval systems often compute aggregate values by processing interesting attributes of large volume databases or data warehouses. The aggregated values are much useful to perform analysis.