07-external-databases.Rmd

# External databases {#external-databases}
Researchers require to add extra information into their data analysis. This is usually extra annotation or even data from an external source (i.e. database). This is effectively a join between two data sets.

The __data step__ called __join left__ and __join right__ are used for this. The extra data requires to be uploaded first. This is done using the standard method of uploading to Tercen.

<center>![](images\workflow_join.png)</center>

A common key or keys are required to join the two data sets.

Once joined the extra annotations or data are available for any succeeding __step__.

<center>![](images\database.png)</center>