Complex joins
The terms simple join and complex join mean different things in different contexts. For our purposes, we will consider a simple join to be a single join between two tables. Every other instance of joining will be considered complex.
Let's look at a star schema as an example of a complex join:
A star schema consists of a fact table referencing one or more dimension tables. The fact table typically contains measures, whereas dimension tables, as the name suggests, contain dimensions. Star schemas are an important part of data warehousing, since their structure is optimal for reporting.
The star schema pictured is based on the Adventure Works data warehouse for MS SQL Server 2014. The workbook associated with this chapter does not include the SQL Server database. Also, to keep the file size of the workbook small, the extract has been filtered to only include data for the United Kingdom. Access to the database may prove helpful when working through some of the exercises in this...
