Relations create relationships between rows, linking their data across tables.
About Relations
In a Glide app, every row in your tables represents an item that then appears in the components in your app.
Each item has its own properties. These are represented as columns in the same table. For example:
A Room can have a: Number, Floor, Extension, Desks, Image
An Employee can have a: Name, Number, Email, Image
A Product can have a: Name, SKU, Image, Price, Description
In some cases, an item can contain an item from another table. These are represented as columns across multiple tables. For example:
A Room has an Occupant
An Employee has a Manager and an Office
A Product has a Category
When an item contains other items, they each have their own set of properties and exist as independent rows in tables. They can then be connected by building relations.
Single vs Multiple Relations
Relations fall into two categories: single relations and multiple relations.
A single relation create a one-to-one relationship. This means one item relates to just one other item. For example, a staff member has a location they work from, or a product has one warehouse it's stored in.
Multiple relations show a one-to-many relationship. This is where one item relates to multiple other items. For example, a manager oversees multiple staff members, or a product belongs in multiple categories.
Creating relations in Glide
In Glide, you can create relations between values using a Relation column. With this column, you specify the type of relation you want—single or multiple. Your app then applies the relation to the values and tables specified.
Check for matching values
Before adding a Relation column, you must first check that the values match in the columns that will be connected. Items cannot be linked together unless they match.
For example, a relation can be created for an employee directory that has a Staff table and a Locations table. In the Staff table, make sure there's a column for the name of the employee's Location. In the Locations table, make sure there's a column for the name of the location that can be tied to the Staff table. By connecting this information, you can integrate it into components or even link to their location in their profile.
Even if the columns have different names in each table, the values in them are shared.
After determining that there are matching values, you can build single or multiple relations using the Relation column.
Building Single Relations
To create a single relation:
In the Data Editor, open the table you want to edit.
Add a new column by clicking the plus symbol to the right of the table.
New columns added with the plus button will always appear on the right. If you'd like to add a column somewhere else in your data, you can select the dropdown menu on an existing column and choose Add column right. You can also click and drag columns to rearrange them.
Name the column.
For Type, search for Relation or navigate to Computed -> Relation.
Specify the values to be matched. Values must match exactly to create a relation. The values in the column will automatically populate when a match is found. If they still appear empty after selecting both columns, the values in the columns do not match and a relation cannot be established.
Click on Done to add the new column to the table.
Building Multiple Relations
To create a multiple relation:
In the Data Editor, open the table you want to edit.
Add a new column by clicking the plus (+) symbol to the right of the table.
New columns added with the plus button will always appear on the right. If you'd like to add a column somewhere else in your data, you can select the dropdown menu on an existing column and choose Add column right. You can also click and drag columns to rearrange them.
Name the column.
For Type, search for Relation or navigate to Computed -> Relation.
Specify the values to be matched. Values must match exactly to create a relation. The values in the column will automatically populate when a match is found. If they still appear empty after selecting both columns, the values in the columns do not match and a relation cannot be established.
Enable the Match multiple option.
Click on Done to add the new column to the table.
Using Relations
The most common use for a Relation column in Glide is to display a single related item or list of items. This is done with Collections.
With that said, you may find more advanced ways to use multiple relations, such as in Choice Components or as the source for the data displayed in Charts.