In Coda, there are two primary ways you can connect tables together:

You'll use this if you want to create a dropdown menu that pulls information from another table. For example, a list of projects associated with tasks, or objectives associated with key results. To create a lookup column:

If you don't see the values you expect when you click the dropdown, head to the table you're looking up from and make sure that the display column is set to the column you want. You'll know something is a display column when it has this icon:

To change the display column, click the column dropdown and choose Set as display column:

Sometimes when you add a new column, you know right from the start that it would be best for its values to lookup into a new table.  

Just click the + button to add a new column, and choose Create new table from the Lookup menu.  You'll get the same options for what to name the table and where to put it, and stay right where you were.   And you can add new values directly from the table you're working in.

Once you have a lookup column, it's now easy to jump to its source table when you need to see or edit its values.  Just open the format column dialog, and choose Open table.

Lookup columns in Coda are full of row references. So for example, the [Assigned to] column in the Tasks table below is full of references to the Team Member table below it. You can add columns that then get properties from those references - e.g. =[Assigned To].[Phone number].

The lookup formula on the other hand, allows you to understand more about items in your tables based on information throughout your doc.  For example, I may want to see a list of all the projects associated with a Goal. If you want to slice and dice your data along multiple factors, check out the filter formula.

The lookup formula has three parts:

In the example below, we want to see all of the contacts associated with the Companies:

Since lookup columns pull all of the details about a row, you can actually use formulas with them by typing  the column name, a dot (or period), and the value want to pull from the other table.

In the example above, we're saying to show the email address of the Contact.

And, to save you time, you don't even have to type a formula. When you create a new column, you'll see the option to create new columns based on what you already have in the table:

A common pattern is to do a reverse lookup - You may want to find out for every Team Member, which tasks are assigned to that member, or what is the total duration of the tasks they have signed up for. Or perhaps you want to summarize your table data. We've created a dedicated article just for this common tool, so check that out here.

Since lookups pull all of the metadata, you may want to see all of that information in a table view. To do so, open the row by clicking the Expand row icon:

Then click the pencil icon to edit the layout:

Make sure the lookup column is visible and not in the "hidden columns" section.

Finally, toggle on Display as table:

Need some real-life examples? Check out the Gallery for tips and tricks.