To fulfill the objectives of data warehouse, a number of front-end tools and back-end tools are required. Front-end tools include analysis, OLAP queries, reporting, data mining etc, while back-end tools include data cleaning, data loading and refreshing etc. Vendor specific Structured Query Language (SQL) engines like Oracle, MS SQL Server, IBM DB2 provide data warehousing facility. However, small and medium enterprise cannot take the advantages of the vendor provided DBMS due to its high Total Cost of Ownership (TCO). As a result open-source SQL engines are becoming popular nowadays. But open-source SQL engines have still no generalized data warehousing facility. In this book it is shown that how to develop a back end tool for loading data into data warehouse from many sources using open source Structured Query Language (SQL) engine MySQL. In this book it is also shown that how to test data loading into data warehouse using the developed back-end tool where data sources are multiple operational MySQL data-bases connected through computer network or backup databases stored in non-volatile media like CD, VCD, pen drive etc.