--- title: "9: Graph dependencies | SurrealDB University" description: "RELATION tables depends_on and activity_of, RELATE, and COMPUTED followed_by." url: https://surrealdb.com/learn/schemas/page-09 --- ![Course content preview](https://surrealdb.com/assets/static/course-schemas.D4CFbBhP.avif) [Back to Courses](https://surrealdb.com/learn) Course chapters [Schema internals and migrations](https://surrealdb.com/learn/schemas) Internals [1: Schemaless vs. schemafull](https://surrealdb.com/learn/schemas/page-01) [2: Schema internals](https://surrealdb.com/learn/schemas/page-02) [3: Migrations](https://surrealdb.com/learn/schemas/page-03) [4: Data types](https://surrealdb.com/learn/schemas/page-04) [5: Automation](https://surrealdb.com/learn/schemas/page-05) Migrations [6: SurrealKit and the first table](https://surrealdb.com/learn/schemas/page-06) [7: Activities and seed data](https://surrealdb.com/learn/schemas/page-07) [8: Computed and asserted fields](https://surrealdb.com/learn/schemas/page-08) [9: Graph dependencies](https://surrealdb.com/learn/schemas/page-09) [10: Sync vs rollouts](https://surrealdb.com/learn/schemas/page-10) [11: Milestones](https://surrealdb.com/learn/schemas/page-11) [12: People and indexes](https://surrealdb.com/learn/schemas/page-12) [13: Events and CI](https://surrealdb.com/learn/schemas/page-13) [14: Capstone](https://surrealdb.com/learn/schemas/page-14) # 9: Graph dependencies Project schedules are inherently a graph: activities depend on other activities, and activities belong to projects. SurrealDB models that with `RELATION` tables and `RELATE`, not just `record<>` fields. This chapter uses `watch`, so each schema save applies without you running another one-shot sync. Start it in a separate terminal before making any changes: ```bash surrealkit sync --watch --user root --pass secret --ns main --db main ``` Leave it running while you add the files below. Stop it with Ctrl+C once you reach the checkpoint, before part [10](https://surrealdb.com/learn/schemas/page-10)’s rollout material. ## `depends_on`: activity → activity Create the file `database/schema/depends_on.surql` and add the following: ```surql DEFINE TABLE depends_on SCHEMAFULL TYPE RELATION IN activity OUT activity; ``` This edge means "the `out` activity has to finish before the `in` activity can start". Run this edge now in SurrealDB Studio or `surreal sql`, and append the same line to `database/seed/demo_project.surql` for the next fresh `seed`. Re-running `surrealkit seed` would replay the whole file and fail on the existing `CREATE` records (part [7](https://surrealdb.com/learn/schemas/page-07)). ```surql RELATE activity:concrete->depends_on->activity:kickoff; ``` SurrealDB Studio's designer can create `RELATION` tables too (part [2](https://surrealdb.com/learn/schemas/page-02)); here we keep them in schema files for SurrealKit. ## `activity_of`: activity → project Create `database/schema/activity_of.surql` and add the following: ```surql DEFINE TABLE activity_of SCHEMAFULL TYPE RELATION IN activity OUT project; ``` Same pattern: run the links now, and append them to `database/seed/demo_project.surql` for the next from-scratch seed. ```surql RELATE activity:kickoff->activity_of->project:one; RELATE activity:concrete->activity_of->project:one; ``` ## COMPUTED `followed_by` (backlinks) The docs sample exposes dependents through a graph `COMPUTED` field: ```surql DEFINE FIELD followed_by ON activity COMPUTED <-depends_on<-activity; ``` Add this line to `activity.surql` and save; `watch` should re-sync within a few seconds. The edge was `RELATE activity:concrete->depends_on->activity:kickoff`, so `kickoff` is the dependency and `concrete` depends on it. Traversal `<-depends_on<-activity` walks inbound `depends_on` edges: from an activity, it finds records that point *at* it. Query the dependency, not the depender: ```surql SELECT name, followed_by.{ name, progress } FROM activity:kickoff; ``` That returns `concrete` under `followed_by`: activities that follow after kickoff (that list kickoff as a dependency). The same field on `activity:concrete` is empty until something depends on concrete. This is the project-planning version of "computed backlinks" from the sketch pages: graph traversal declared right in the schema. ## Graph queries ```surql -- Dependencies leaving an activity SELECT ->depends_on->activity.{ name, start, end } FROM activity:concrete; -- Everything tied to a project SELECT name, ->activity_of->project AS project, ->depends_on->activity AS depends_on FROM activity; ``` For larger graphs, add indexes in part [12](https://surrealdb.com/learn/schemas/page-12) to support range and lookup patterns. ## RELATION vs record field | Approach | When to use | | --- | --- | | `record` on `activity` | Simple foreign key, one project per record | | `activity_of` `RELATION` | Explicit graph, multiple routing queries, edge metadata later | | Both | Valid during expand migrations; pick one canonical model and contract the other (parts [10](https://surrealdb.com/learn/schemas/page-10)–[11](https://surrealdb.com/learn/schemas/page-11)) | The docs sample uses `RELATE` for membership, and this course follows that. ## Checkpoint - `depends_on` and `activity_of` `RELATION` tables in schema files - Seed data uses `RELATE` - `COMPUTED` `followed_by` for successor lookup (who depends on this activity) When the graph looks right, stop `watch` with Ctrl+C so the terminal is free for part [10](https://surrealdb.com/learn/schemas/page-10)’s rollout material (then milestones in part [11](https://surrealdb.com/learn/schemas/page-11)). Next: sync vs rollouts, why shared databases need a different SurrealKit command, then milestones that roll up activity `progress`. Previous 8: Computed and asserted fields [Previous](https://surrealdb.com/learn/schemas/page-08) Next lesson 10: Sync vs rollouts [Next lesson](https://surrealdb.com/learn/schemas/page-10) ```json {"@context":"https://schema.org","@type":"Course","name":"Schema internals and migrations","description":"Learn how SurrealDB stores schema metadata, how DEFINE statements shape your database, and how to migrate production data safely.","url":"https://surrealdb.com/learn/schemas","inLanguage":"en","isAccessibleForFree":true,"provider":{"@type":"Organization","name":"SurrealDB","url":"https://surrealdb.com"},"hasPart":[{"@type":"LearningResource","name":"Schema internals and migrations","url":"https://surrealdb.com/learn/schemas"},{"@type":"LearningResource","name":"1: Schemaless vs. schemafull","url":"https://surrealdb.com/learn/schemas/page-01"},{"@type":"LearningResource","name":"2: Schema internals","url":"https://surrealdb.com/learn/schemas/page-02"},{"@type":"LearningResource","name":"3: Migrations","url":"https://surrealdb.com/learn/schemas/page-03"},{"@type":"LearningResource","name":"4: Data types","url":"https://surrealdb.com/learn/schemas/page-04"},{"@type":"LearningResource","name":"5: Automation","url":"https://surrealdb.com/learn/schemas/page-05"},{"@type":"LearningResource","name":"6: SurrealKit and the first table","url":"https://surrealdb.com/learn/schemas/page-06"},{"@type":"LearningResource","name":"7: Activities and seed data","url":"https://surrealdb.com/learn/schemas/page-07"},{"@type":"LearningResource","name":"8: Computed and asserted fields","url":"https://surrealdb.com/learn/schemas/page-08"},{"@type":"LearningResource","name":"9: Graph dependencies","url":"https://surrealdb.com/learn/schemas/page-09"},{"@type":"LearningResource","name":"10: Sync vs rollouts","url":"https://surrealdb.com/learn/schemas/page-10"},{"@type":"LearningResource","name":"11: Milestones","url":"https://surrealdb.com/learn/schemas/page-11"},{"@type":"LearningResource","name":"12: People and indexes","url":"https://surrealdb.com/learn/schemas/page-12"},{"@type":"LearningResource","name":"13: Events and CI","url":"https://surrealdb.com/learn/schemas/page-13"},{"@type":"LearningResource","name":"14: Capstone","url":"https://surrealdb.com/learn/schemas/page-14"}]} ``` ```json {"@context":"https://schema.org","@type":"LearningResource","name":"9: Graph dependencies","description":"RELATION tables depends_on and activity_of, RELATE, and COMPUTED followed_by.","url":"https://surrealdb.com/learn/schemas/page-09","learningResourceType":"lesson","isPartOf":{"@type":"Course","name":"Schema internals and migrations","url":"https://surrealdb.com/learn/schemas"},"position":12} ``` ```json {"@context":"https://schema.org","@type":"Organization","name":"SurrealDB","url":"https://surrealdb.com","logo":"https://surrealdb.com/assets/static/logo.BG7_TG2b.svg","description":"SurrealDB is the unified data layer for AI. 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