Live vs Extract

LIVE CONNECTION

This refers to a data source which contains direct connections to the real-time data.
Live connections can be used at a place where the data is real-time data which when get updated, so our visualization also gets updated automatically.
EXAMPLE– real time transactions.
Live connections are slower for complex visualizations.
Live connections are used especially in less complex visualizations with small data sets, filters, calculations etc.
Live connections get refreshed when there is a change in the original data source.
Live connections always rely on the database for all queries.
A Live connection in Tableau basically means that Tableau is querying and reading directly from your database.

Extract files are the local copy of the data source that you can use to make the view.
Extracts can be used at a place where the view can be created by a subset of the data source.
EXAMPLE– Keeping the record of the monthly trends of a hospital.
Extracts are much faster for visualization.
Extracts are used especially in more complex visualizations with large datasets, filters calculations etc.
Extract is a snapshot of the data, so they need to be refreshed to receive updates from the original data source.
However extracts databases should not always be optimized.
The extracts in tableau are refreshed in two ways:-

A refresh in which only the rows and columns are added which are new since the previous time you extracted the data.
Most data sources support an instrumental refresh as it takes less time.
Although it is faster but once in a period of time the user needs to use the full refresh to ensure that the data is most up to date.

It refers to the refreshment of the entire extract
In this refresh, all of the rows are replaced with the data in the original data source.
This kind of refresh ensures that the user has an exact copy of the original data.
A full refresh can sometimes take a long time & be expensive on the database.

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