Summary

SQL Server is a relational database management system, but that does not mean we can rely only on data inside SQL Server for our analysis. There are several services and components in SQL Server that allow us to access data in structured, semi-structured, or even an unstructured form, and either query such data directly in its original storage (external to SQL Server) or import the data into SQL Server and transform the data into a relational form for further processing and wrangling with other existing datasets. Since the data coming into SQL Server may have different formats and can come from reliable and less reliable data sources, you need to carefully check the data during the cleaning phase so that you'll not import wrong, missing, or duplicate values to your database.