Data Blending

Data blending is used when we use data from more than one data source in a single workbook. Data blending is based on the common dimension used to join both databases. Two data sources used in data blending are referred to as a primary data source and secondary data source. A small chain image appears next to the common dimension between both data sources. Data blending is used to combine data from one data source with column data from another data source in a single table.

Why data blending is useful over join-

1- Data is at different granularity.
2- Data is not supported by cross-database join

Tableau Data Extract

Tableau data extract (.dte) Stores tableau data as a filtered and aggregated extract. TDE files are data extracted from external sources such as MS Access or Excel. It is used for external data.  This data can be text,  numerical, or statistical data. 

TDE extracts are Tableau's method of caching data logically to reduce database hits for frequent access reports. TDE extract can be refreshed manually through the Tableau desktop or can be scheduled for periodic refresh through the enterprise edition.