Quick Tips in Pics #1: Cross-Database Joins

by Megan Hunt

When you try to join two or more different datasets in Tableau you will see some handy join options in the form of Venn Diagram. But what do they really mean?  Here’s a quick, handy guide.

Cross-Database Joins at a Glance

Don’t forget! Joining across databases joins at the row level.  If you want to join on aggregated results then use Blending.  You can read more about the difference on Rachel Costa’s blog.

join-on-tableau-screen

First pick your individual Primary Data Source column headers and match those headers across to your Secondary Data Source column headers.

inner-join

Inner Join

Picks up:
ONLY where the field names match in both datasets.
(i.e. you could fail to bring in some data if not careful!)

 

 

left-join

Left Join

Picks up:
ALL Primary field names and only those that match from the Secondary dataset.

 

 

right-join

Right Join

Picks up:
ALL Secondary field names and only those that match from the Primary dataset.

 

 

full-outer

Full Outer

Picks up:
ALL Primary field names and ALL Secondary field names. You may find Nulls where things don’t match but all the data will be there.

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