Single Relation:
What it is:
Matches a value in one column with the FIRST value found in a different column.
What it does:
Creates a one-row to one-row link between the two columns
What to do next: Display the relation using the Relation component or use a lookup column to grab a value from any column in the matching row.
Multiple Relation:
What it is:
Matches a value in one column with ALL values found in a different column.
What it does:
Creates a one-row to many-row link between the two columns
What to do next:
- Display the multiple relation using an inline list component
- Use a Rollup column to grab a count/sum/average/etc of numeric values of a column in all matching rows
- Use a Join column to concaténate the values of a column in all matching rows
Example:
One table of users. One table containing user reviews. Each table has an email column.
User table:
Create a MULTIPLE relation column linking the email column in the users table to the email column in the user reviews table.
What this allows: on the user profile, create an inline list sourced by the relation that will display all reviews left by that user
User Reviews table:
Create a SINGLE relation column linking the email column in the user reviews table to the email column in the user table.
Create a lookup column that uses the single relation to find the user’s name from the users sheet.
Create additional lookup columns to find user photo or any other data found in the user table.
What this allows:
On a User Reviews screen, display the name and photo of the user that made the review.
Typically, you create relations between two different tables. Sometimes, you can use them to create a link within the same table, but this is usually an edge case.