When you create a Relation property in Notion, it starts as a one-way link by default. This means a record in Database A can point to a record in Database B, but Database B does not show the connection back. You need a two-way relation so that both databases display the linked records. This article explains how to convert a one-way relation to a two-way relation using the Relation settings.
A one-way relation is useful when you only need to reference data from another database without tracking the reverse connection. However, many workflows require both sides to see the link, such as a project management system where tasks link to clients and clients show all their tasks. Notion provides a toggle in the Relation property editor to enable the reverse direction.
This guide covers the exact steps to turn a one-way relation into a two-way relation. It also explains what happens to existing data, how to avoid duplicate properties, and what to do if the reverse relation does not appear.
Key Takeaways: Converting One-Way to Two-Way Relations
- Relation property > Edit property > Show on [Database B]: Toggle this switch to create the reverse relation in the target database.
- Rollup property is optional: A Rollup can be added to the reverse relation to calculate or display data from the original database.
- Existing links remain intact: All current one-way links are automatically converted to two-way links when you enable the toggle.
How a One-Way Relation Works Versus a Two-Way Relation
A one-way relation in Notion is created when you add a Relation property to a database and select a target database. For example, you have a Tasks database and a Projects database. You add a Relation property called Project in the Tasks database. Each task can link to one project. But the Projects database has no column showing which tasks are linked to it. The relation is one-way.
A two-way relation adds a matching Relation property in the target database automatically. In the example above, enabling two-way creates a Tasks property in the Projects database. Every project now shows a list of tasks linked to it. Both databases can be used as the starting point for viewing linked records.
Notion stores the underlying link data in a single internal table. The toggle simply shows or hides the reverse property. No duplicate data is created. The reverse property name is generated by Notion based on the original property name. You can rename it after creation.
Steps to Convert a One-Way Relation to a Two-Way Relation
Follow these steps to enable the reverse relation. You need edit access to both databases.
- Open the Relation property in the source database
Go to the database that contains the one-way Relation property. Hover over the column header of that property. Click the downward arrow that appears, then select Edit property from the menu. - Locate the Show on toggle
In the Edit property window, look for the section labeled Show on [Database B name]. This is a toggle switch. The label shows the name of the target database. For example, if your target database is called Projects, the toggle reads Show on Projects. - Toggle the switch to enable two-way
Click the toggle so it turns blue. Notion immediately creates a new Relation property in the target database. The property name is the name of your source database. For instance, if the source database is Tasks, the new property is named Tasks. All existing links become visible in both directions. - Rename the reverse property if needed
Navigate to the target database. Find the new Relation property. Hover over its column header, click the arrow, and select Edit property. Change the name to something more descriptive, such as Linked Tasks. The reverse property functions exactly like any other Relation property. - Optionally add a Rollup to the reverse property
If you want to display data from the source database in the target database, add a Rollup property. Open the reverse property settings, click Add a Rollup, and choose the property from the source database to aggregate. For example, you can show the total hours logged for all tasks linked to a project.
What to Avoid When Converting One-Way Relations
You cannot undo the two-way conversion without deleting the property
There is no toggle to turn a two-way relation back into a one-way relation. If you disable the reverse property by deleting it, the original one-way relation remains. But you cannot simply hide the reverse column. The only way to remove the reverse property is to delete it entirely from the target database. This does not affect the original links in the source database.
Do not create a second Relation property manually
Some users try to create a separate Relation property in the target database pointing back to the source database. This creates a duplicate set of links that are not connected to the original relation. You end up with two independent Relation properties that require manual syncing. Always use the built-in toggle instead.
Renaming the source property does not rename the reverse property
If you rename the original Relation property in the source database, the reverse property name in the target database does not update automatically. You must manually rename the reverse property. This is a common source of confusion when databases are heavily linked.
One-Way Relation vs Two-Way Relation: Key Differences
| Feature | One-Way Relation | Two-Way Relation |
|---|---|---|
| Reverse property created | No | Yes, automatically |
| View linked records from target database | Not possible | Possible |
| Data duplication | None | None (same underlying link) |
| Storage impact | Minimal | Minimal (only one property column added) |
| Use case | Simple reference, no need for reverse lookup | Bidirectional tracking, e.g., tasks and projects |
Converting a one-way relation to a two-way relation takes less than 30 seconds. The toggle in the Edit property window is the only tool you need. After conversion, both databases show linked records. You can rename the reverse property and add Rollups to display calculated data from the other side. This feature is available on all Notion plans, including the Free plan.