We have singled out this resource as an introduction to data quality and data profiling, even though it is in fact a documentation set for an open source tool, DataCleaner. The first section of this documentation gives a good introduction to data profiling and data quality. The rest of the documentation is worth reading, even though you may not use the tool, as it gives an insight into data profiling tool capabilities. The tool itself is listed in our Data quality testing tools category.