# How to Connect Notion Databases with Relations and Rollups

> Relation vs rollup, one-way vs two-way, every rollup calculation, six recipes (Percent checked progress bar, counts, sums, dates, linked views) and the limits Notion's help is quiet about.

- Source: https://ivgraph.com/journal/notion-database-relations/
- Author: [Andrii Danylchenko](https://ivgraph.com/team/#Andrii-Danylchenko), Founder / CTO, IVGraph
- Published: 2026-07-30; updated: 2026-10-15
- Type: Guide
- About: Notion ([Wikidata Q60747998](https://www.wikidata.org/wiki/Q60747998))
- Mentions: Backlink ([Wikidata Q373952](https://www.wikidata.org/wiki/Q373952)); [IVGraph](https://ivgraph.com/)

## TL;DR

A **relation** links pages in one Notion database to pages in another (each Task → its Project). A **rollup** calculates over those links (each Project → percent of its tasks done). Add a Relation property, switch on *Show on [database]* if both sides should see the link, then add a Rollup and pick a calculation. The classic example: a rollup of a Done checkbox with *Percent checked*, displayed as a bar, gives every project a progress bar. Rollups reach one relation away and can't roll up another rollup.

## Relation vs Rollup in One Minute

A **relation** is a database property whose values are pages from another database. A text column holds words; a relation column holds live links: each Task points at its Project, each Meeting note at its Client. Notion's own help uses Customers and Items Purchased: one relation, readable from both sides.

A **rollup** is a property that looks through a relation and calculates something from the related pages: how many tasks a project has, what percent of them are done, how much a customer has spent, when you last met a client. No relation, no rollup.

|  | Relation | Rollup |
| --- | --- | --- |
| What it stores | Links to pages | A calculated value (or the related values as they are) |
| Editable in the cell | Yes: pick or remove pages | No: it updates when related pages change |
| Needs | A target database | A relation + a property of the related pages |
| Example | Task → Project | Project → 60% of tasks done |

Both sit in the same property menu as Text, Number, Select, Status, Date, Formula, Checkbox, Person, Files & media, URL, Email, Phone, Button, ID, Place and the created/edited stamps. They are the two property types built specifically for working across databases.

## Creating a Relation, Step by Step

1. In your database (say, Tasks), click **+ New property** and choose **Relation**.
2. Pick the database to link to (Projects). Notion shows a preview of the new property.
3. Decide whether the other database should see the link too (the toggle **Show on Projects**, see below).
4. Optionally limit the property to **1 page** instead of **No limit**: useful when every task belongs to exactly one project.
5. Click **Add relation**. Each cell in the new column now opens a search of pages from Projects; the **–** next to a page removes the link.

### One-way vs two-way relations

Relations are **one-way by default**: Tasks get a Project column, but Projects don't get a Tasks column. Switch on **Show on [related database]** and name the mirrored property to make it **two-way**. From then on, a project picked in a task's cell also shows that task in the project's cell, and the other way round. You can switch this on later for an existing relation in the same settings.

- **Two-way** when both sides need the link: Projects ↔ Tasks, Clients ↔ Meetings. A rollup on Projects needs a relation property on Projects, so for progress bars and counts the link must be two-way (or created from the Projects side).
- **One-way** when the other database would only get clutter: many note databases pointing at one shared Sources or Tags database.

> **Duplicating breaks the mirror.** When you duplicate a database that has a two-way relation, Notion turns it into a one-way relation in the copy. You can switch it back to two-way.

If you build databases through the API or let an AI agent do it over [Notion MCP](https://ivgraph.com/journal/notion-mcp/), the same choice appears as `single_property` (one-way) or `dual_property` (two-way) in the relation property's definition.

### Relate a database to itself: sub-items and dependencies

When creating a relation, you can pick the current database; it shows up as **This database**. With **Two-way relation** off you get one property that works in both directions (good for "Related notes"). With it on you get a pair, such as "Next task" and "Previous task". Self-relations are how a flat notes table quietly becomes a knowledge network.

Notion packages two self-relation patterns as ready-made features, both under **Database settings → More settings**:

- **Sub-items** → **Turn on sub-items**: tasks nest under parent tasks right in the table. Under **Advanced settings** you choose which property drives the nesting and whether sub-items or parent items are nested.
- **Dependencies** → **Turn on dependencies**: tasks that block other tasks, drawn as connections in timeline view. You also choose how dates shift: **Shift only when dates overlap**, **Shift & maintain time between items**, or **Do not automatically shift**, with an **Avoid weekends** toggle.

## Rollups: Every Calculation Option

Add a property, choose **Rollup**, then make three choices: which *relation* to look through, which *property* of the related pages to read, and how to *calculate*. Since April 2026, rollups also take number formatting (currency, percent and so on) and decimal places directly.

| Calculate | Works on | Typical use |
| --- | --- | --- |
| Show original | Any property | Show the related page's value as is (a task shows its project's deadline) |
| Show unique values | Any property | All tags used across a project's tasks, without repeats |
| Count all · Count values · Count unique values | Any property | How many related pages or values there are |
| Count empty · Count not empty · Percent empty · Percent not empty | Any property | How many tasks still have no owner or no date |
| Checked · Unchecked · Percent checked · Percent unchecked | Checkbox | Done vs not done; Percent checked is the progress bar |
| Count per group · Percent per group | Status | Tasks in the Complete group, as a count or a share |
| Sum · Average · Median · Min · Max · Range | Number | Total spend, average estimate, biggest invoice |
| Earliest date · Latest date · Date range | Date | First and last meeting, project span |

Sorting a view by a rollup works only when the rollup returns a number. For a total across the whole database (not per row), you don't need a rollup: click the property and use **Calculate** (for example, Sum).

## Six Relation and Rollup Recipes

All six assume a working relation; recipes 1–4 need it to be visible on the database where you add the rollup (two-way, or created from that side).

### 1. Project progress bar with Percent checked

1. Projects ↔ Tasks are related two-way; Tasks have a **Done** checkbox.
2. In Projects, add a **Rollup** called Progress: relation **Tasks**, property **Done**, calculate **Percent checked**.
3. In the rollup's settings, display it as a **bar** (or **ring**) instead of a plain number.

Tracking tasks with a **Status** property instead of a checkbox? Roll up Status with **Percent per group** and choose the **Complete** group. More bar recipes (formulas, star ratings) and a free embeddable bar with a deadline countdown for dashboards are on our [Notion progress bar page](https://ivgraph.com/notion-widgets/progress-bar/).

### 2. Count open tasks per project

Rollup on Projects: relation **Tasks**, property **Status**, calculate **Count per group** and pick the group you care about (In progress, To-do). For the plain number of tasks, use **Count all** on any property.

### 3. Sum: customer lifetime spend

Customers ↔ Orders. Rollup on Customers: relation **Orders**, property **Amount**, calculate **Sum**, format as currency. Swap Sum for **Average** or **Max** to get average or biggest order. The same pattern gives hours per project (Tasks → Estimate → Sum).

### 4. Last contact date per client

Clients ↔ Meetings. Rollup on Clients: relation **Meetings**, property **Date**, calculate **Latest date**. Now every client row shows when you last met, so the ones you haven't talked to in a while stand out. **Earliest date** gives the first meeting; **Date range** gives the span.

### 5. Show a related page's property on the row

You want each task to show its project's deadline without opening the project. Rollup on Tasks: relation **Project**, property **Deadline**, calculate **Show original**. Now you can see (though not sort by) the project deadline in the Tasks table.

### 6. Show only a project's tasks on its page (linked database)

A **linked database** is a view of an existing database placed on another page. Edits made in it go to the original database; its filters, sorts and views stay local and don't change the original. To add one, type **/linked** on the page, pick the database, then copy an existing view or create a new one. Notion's newer help calls this linking an existing data source: **/database** → **Link to existing data source**.

1. Open a project page and add a linked view of **Tasks**.
2. Add a **Filter** on the **Project** relation: **contains** → this project.
3. The page now lists only its own tasks. Checking Done here updates the Tasks database and, with it, the project's progress rollup.

### When a rollup can't filter: use a formula

A rollup has one calculation and no filter: it can't count "only meetings after today". Formulas can read related pages directly since Formulas 2.0. For upcoming meetings per client:

```
prop("Meetings").filter(current.prop("Date") > now()).length()
```

## Where Relations and Rollups Hit Their Ceiling

- **One hop only.** A rollup reads pages one relation away, and Notion doesn't support rolling up a rollup (its help says this avoids unintended loops). For Client → Project → Tasks answers, add a direct relation or restructure.
- **Export loses the links.** In a CSV export, relation properties become plain-text URLs, and importing that CSV doesn't restore the relations.
- **You see cells, not structure.** A relation column shows links one row at a time. Nobody can look at three related databases and say what the overall network looks like.
- **Auditing is manual.** Which projects have no notes? Which notes connect to nothing? Rollups count per row; there's no workspace-level view of connection health.
- **Complexity hides.** Mature workspaces collect dozens of relations; the model in your head and the model in the schema drift apart without anyone noticing.

## Relations Are Edges: See Them That Way

Everything a relation encodes is graph data: pages are nodes, and relations (plus [backlinks](https://ivgraph.com/journal/notion-backlinks/), @-mentions and sub-page nesting) are edges. Notion itself shows none of this as a map, as we covered in [Does Notion Have a Graph View?](https://ivgraph.com/journal/does-notion-have-graph-view/)

IVGraph reads your workspace through the official API and draws that structure: the Projects ↔ Tasks ↔ Notes triangle from your [second brain](https://ivgraph.com/journal/notion-second-brain/) becomes a visible shape, with hubs, clusters and unconnected pages in plain sight. Use it in 3D in the app, or embed a 2D [graph view widget](https://ivgraph.com/notion-widgets/graph-view/) inside a Notion page.

![A project page selected in IVGraph: its properties (parent, status, owner) and 47 connections to tasks, bugs, releases and meeting notes](https://ivgraph.com/assets/img/shots-2026-10/graph-node-card-1440w.webp)

*Relations as edges: the properties Notion shows in columns, and the related tasks, bugs and notes drawn as lines from one project page.*

## FAQ

### What is the difference between a relation and a rollup in Notion?

A relation is the link: a property whose values are pages from another (or the same) database, like each Task pointing to its Project. A rollup is a calculation that reads through that link, like a Project showing how many of its tasks are done. A rollup always needs an existing relation.

### How do I make a Notion relation two-way?

In the relation property's settings, switch on the toggle Show on [name of the related database], name the matching property and confirm. Both databases then have a relation property, and a link added on one side appears on the other.

### How do I show the percent of done tasks as a progress bar in Notion?

Relate Projects to Tasks, give Tasks a Done checkbox, then add a Rollup to Projects: relation Tasks, property Done, calculation Percent checked. Set the rollup to display as a bar or ring instead of a number. If you track tasks with a Status property, use Percent per group and pick the Complete group.

### Can I roll up a rollup in Notion?

No. Notion's help says rollups of rollups are not supported, to avoid unintended loops. A rollup reads properties of pages one relation away; for a two-hop answer, add a direct relation between the two databases.