Joins
Upon opening the join Gem, you can see a pop-up which provides several helpful features.
For transparency, you can always see the (1) Input schema on the left hand-side, (2) Errors in the footer, and have the ability to (3) Run the Gem on the top right.
To fill-in our (5) Join condition within the (4) Conditions section, start typing the input table name and key. For example, if we have two input tables, nation and customer, type nation.nationkey = customers.nationkey. This condition finds a nation based on the nationkey feild for every single customer.
When you’re writing your join conditions, you’ll see available functions and columns to speed up your development. When the autocomplete appears, press ↑, ↓ to navigate between the suggestions and press tab to accept the suggestion.
Select the (6)Join Type according to the provider, eg Databricks or Snowflake.
The (7) Expressions tab allows you to define the set of output columns that are going to be returned from the Gem. Here we leave it empty, which by default passes through all the input columns, from both of the joined sources, without any modifications.
To rename our Gem to describe its functionality, click on it’s (8) Name or try the Auto-label option. Gem names are going to be used as query names, which means that they should be concise and composed of alphanumeric characters with no spaces.
Once done, press (9) Save.
To learn more about the Join Gem UI, see this page which illustrates features common to all Gems.
Add a port
It's easy to add an extra source to a Join Gem. Just connect and configure.
Once the source is (1) connected, click to (2) edit the ports.
Update the (3) port name from the default input in2 to a more descriptive name such as the table name, in this case NATIONS.
Fill in the (4) Join condition for the new table and specify the (5) Join type.
Click (6) Save.
Run
When your Join Gem has the desired inputs, conditions and expressions, (7) run interactively to view (8)sample data.