Relations & database linking

2sync can map external data to Notion Relations, enabling powerful connections between your synced items and other databases. Link calendar attendees to contacts, tasks to projects, or emails to CRM records.

What is relation mapping?

Relations in Notion link pages across databases. 2sync extends this by automatically creating relations based on synced data.

Without relations:

• Calendar event shows "john@example.com" as text
• No connection to your contacts database

With relations:

• Calendar event links to John Doe's page in Contacts
• Click through to see all interactions with John
• Use rollups to count meetings per contact

How do I set up relations?

Prerequisites

1. Both databases connected to 2sync: The main database AND the related database must have 2sync access
2. Relation property exists: Create a Relation property in Notion pointing to the target database
3. Matching identifiers: Data must match between sources (e.g., email addresses)

Common relation types

Attendees → contacts

Map calendar attendees to a Contacts database:

1. Create a Contacts database connected to 2sync
2. Add a Relation property in your events database → Contacts
3. Map Attendees (Relation) to this Relation property
4. 2sync matches attendee emails to contact records

Result: Click an attendee to see their contact page. Use rollups to count meetings.

Project → projects database

Map Todoist projects to a Notion Projects database:

1. Create a Projects database connected to 2sync
2. Add a Relation property in tasks → Projects
3. Map Project (Relation) to this property
4. Tasks link to project pages

Result: Project pages show all related tasks via backlinks.

Calendar → calendars database

Map calendar names to a Calendars database:

1. Create a Calendars database with entries for each calendar
2. Add a Relation property in events → Calendars
3. Map Calendar Name (Relation) to this property
4. Events link to their calendar page

Result: Filter and organize by calendar with rich calendar metadata.

When should I use relations instead of select?

How do I troubleshoot relation issues?

"Can't create a relation" error

Cause: The target database isn't connected to 2sync.

Fix: Open the target database in Notion, click (•••) > Add connections > 2sync.

Relations not linking

Causes:

• Names don't match exactly (case-sensitive)
• Target page doesn't exist yet
• Permission issues

Fixes:

1. Check spelling and case of project/section names
2. Ensure target pages exist in the related database
3. Verify 2sync has access to both databases

Empty relation field

Cause: The linked value doesn't exist in the target database.

Example: Task has Project "Marketing," but no "Marketing" page exists in Projects database.

Fix: Create the missing page in the target database, or let 2sync create it automatically (for supported relations).

How does automatic entry creation work?

For some relations, 2sync can create entries automatically:

Projects and Sections (Todoist):

• When a task syncs with a new project name
• 2sync creates a corresponding page in the Projects database
• Future tasks link to that page

Requirements:

• Target database must be connected to 2sync
• Relation must be properly mapped

Email sender → CRM

For a full walkthrough on building a Notion CRM with synced contacts, see Create a Notion CRM.

Link Gmail/Outlook emails to a CRM or Contacts database:

1. Sync contacts to a Contacts database
2. Sync emails with From (Relation) mapped
3. Emails automatically link to sender's contact page

Result: Open a contact to see all email correspondence.

Thread relations (email)

Group email threads using relations:

• Thread (Relation): Link emails in the same conversation
• Navigate through email threads in Notion
• See the full conversation history

Setup:

1. Map Thread (Relation) to a self-relation (same database)
2. Or create a Threads database for thread metadata

Calendar relations

Multiple calendars

When syncing multiple calendars:

1. Map Calendar Name (Relation) to a Calendars database
2. Each event links to its source calendar
3. Filter views by calendar relation

Attendees across databases

Link event attendees to:

• Contacts database: Full contact info
• Team directory: Internal team members
• CRM records: External contacts

What are the best practices for relations?

Keep names consistent

Relations match by name. Ensure:

• Project names in Todoist match entries in Projects database
• Calendar names match entries in Calendars database
• Contact emails match between sources

Connect databases first

Before mapping relations, ensure both databases are connected to 2sync. Missing connections are the most common cause of relation failures.

Use self-relations carefully

Self-relations (database relates to itself) work for:

• Parent/child tasks
• Email threads
• Subtask hierarchies

But can create complex setups. Start simple.

Monitor sync status

Map Sync Status to catch relation issues. See Sync item statuses for a full list of states:

• Items failing to link show different statuses
• Helps diagnose problems early

Related

• Notion property types for understanding which property types support relations
• Create a Notion CRM for a step-by-step guide to building a CRM with relations
• Google Contacts fields for fields available when mapping contacts
• Outlook Contacts fields for Outlook-specific contact fields
• How sync works for understanding how relation matching is processed

FAQ