Zuvo Docs

Guide

Querying Joins and Nested tables

The Data APIs automatically detect relationships between Postgres tables.

The data APIs automatically detect relationships between Postgres tables. Since Postgres is a relational database, this is a very common scenario.

One-to-many joins

Use an example database that stores orchestral_sections and instruments:

Tables

Orchestral sections

idname
1strings
2woodwinds

Instruments

idnamesection_id
1violin1
2viola1
3flute2
4oboe2
SQL
create table orchestral_sections (
  "id" serial primary key,
  "name" text
);

insert into orchestral_sections
  (id, name)
values
  (1, 'strings'),
  (2, 'woodwinds');

create table instruments (
  "id" serial primary key,
  "name" text,
  "section_id" int references "orchestral_sections"
);

insert into instruments
  (name, section_id)
values
  ('violin', 1),
  ('viola', 1),
  ('flute', 2),
  ('oboe', 2);

The APIs will automatically detect relationships based on the foreign keys:

JavaScript
const { data, error } = await supabase.from('orchestral_sections').select(`
  id,
  name,
  instruments ( id, name )
`)

TypeScript types for joins

supabase-js always returns a data object (for success), and an error object (for unsuccessful requests).

These helper types provide the result types from any query, including nested types for database joins.

Given the following schema with a relation between orchestral sections and instruments:

create table orchestral_sections (
  "id" serial primary key,
  "name" text
);

create table instruments (
  "id" serial primary key,
  "name" text,
  "section_id" int references "orchestral_sections"
);

We can get the nested SectionsWithInstruments type like this:

import { QueryData, QueryError, QueryResult } from '@supabase/supabase-js'

const sectionsWithInstrumentsQuery = supabase.from('orchestral_sections').select(`
  id,
  name,
  instruments (
    id,
    name
  )
`)
type SectionsWithInstruments = QueryData<typeof sectionsWithInstrumentsQuery>

const { data, error } = await sectionsWithInstrumentsQuery
if (error) throw error
const sectionsWithInstruments: SectionsWithInstruments = data
GraphQL
const Query = `
  query {
    orchestral_sectionsCollection {
      edges {
        node {
          id
          name
          instruments {
            id,
            name
          }
        }
      }
    }
  }
`
URL
GET https://[REF].supabase.co/rest/v1/orchestral_sections?select=id,name,instruments(id,name)

Join types and join modifiers

By default, embedded relations use left join semantics from the parent table:

  • Parent rows are returned even if no related rows match.
  • The embedded relation is [] for one-to-many joins and null for many-to-one joins when nothing matches.

To filter out parent rows that do not match the related table, use !inner on the embedded relation.

What : and ! mean in join syntax

SyntaxMeaningExample
alias:relation(columns)Rename the embedded relation in the response.start_scan:scans(id, badge_scan_time)
relation!inner(columns)Use inner join behavior for that embedded relation.instruments!inner(id, name)
relation!foreign_key(columns)Choose which foreign key relationship to use when multiple foreign keys match the join.scans!scan_id_start(id)

Example data for join types

Tables

Orchestral sections

idname
1strings
2woodwinds
3percussion

Instruments

idnamesection_id
1violin1
2viola1
3flute2
4oboe2
SQL
create table orchestral_sections (
  "id" serial primary key,
  "name" text
);

insert into orchestral_sections
  (id, name)
values
  (1, 'strings'),
  (2, 'woodwinds'),
  (3, 'percussion');

create table instruments (
  "id" serial primary key,
  "name" text,
  "section_id" int references orchestral_sections
);

insert into instruments
  (id, name, section_id)
values
  (1, 'violin', 1),
  (2, 'viola', 1),
  (3, 'flute', 2),
  (4, 'oboe', 2);

Left join (default)

This query filters on a joined field (instruments.name) but still returns all parent rows:

JavaScript
const { data, error } = await supabase
  .from('orchestral_sections')
  .select(
    `
    id,
    name,
    instruments ( id, name )
  `
  )
  .eq('instruments.name', 'flute')
URL
GET https://[REF].supabase.co/rest/v1/orchestral_sections?select=id,name,instruments(id,name)&instruments.name=eq.flute

Result

[
  {
    "id": 1,
    "name": "strings",
    "instruments": []
  },
  {
    "id": 2,
    "name": "woodwinds",
    "instruments": [{ "id": 3, "name": "flute" }]
  },
  {
    "id": 3,
    "name": "percussion",
    "instruments": []
  }
]

Inner join (!inner)

Adding !inner filters out parent rows that don't match the joined filter:

JavaScript
const { data, error } = await supabase
  .from('orchestral_sections')
  .select(
    `
    id,
    name,
    instruments!inner ( id, name )
  `
  )
  .eq('instruments.name', 'flute')
URL
GET https://[REF].supabase.co/rest/v1/orchestral_sections?select=id,name,instruments!inner(id,name)&instruments.name=eq.flute

Result

[
  {
    "id": 2,
    "name": "woodwinds",
    "instruments": [{ "id": 3, "name": "flute" }]
  }
]

Filtering using joined fields

Use joined_table.column in filters (for example eq, neq, and in):

JavaScript
const { data, error } = await supabase
  .from('instruments')
  .select(
    `
    id,
    name,
    orchestral_sections!inner ( id, name )
  `
  )
  .eq('orchestral_sections.name', 'woodwinds')
URL
GET https://[REF].supabase.co/rest/v1/instruments?select=id,name,orchestral_sections!inner(id,name)&orchestral_sections.name=eq.woodwinds

Result

[
  {
    "id": 3,
    "name": "flute",
    "orchestral_sections": {
      "id": 2,
      "name": "woodwinds"
    }
  },
  {
    "id": 4,
    "name": "oboe",
    "orchestral_sections": {
      "id": 2,
      "name": "woodwinds"
    }
  }
]

Many-to-many joins

The data APIs will detect many-to-many joins. For example, if you have a database which stored teams of users (where each user could belong to many teams):

create table users (
  "id" serial primary key,
  "name" text
);

create table teams (
  "id" serial primary key,
  "team_name" text
);

create table members (
  "user_id" int references users,
  "team_id" int references teams,
  primary key (user_id, team_id)
);

In these cases you don't need to explicitly define the joining table (members). If we wanted to fetch all the teams and the members in each team:

JavaScript
const { data, error } = await supabase.from('teams').select(`
  id,
  team_name,
  users ( id, name )
`)
GraphQL
const Query = `
  query {

</TabPanel>
<TabPanel id="graphql" label="GraphQL">

```

javascript
const Query = `
  query {
    teamsCollection {
      edges {
        node {
          id
          team_name
          users {
            id,
            name
          }
        }
      }
    }
  }
`
URL

bash
GET https://[REF].supabase.co/rest/v1/teams?select=id,team_name,users(id,name)

Specifying the ON clause for joins with multiple foreign keys

For example, if you have a project that tracks when employees check in and out of work shifts:


sql
-- Employees
create table users (
  "id" serial primary key,
  "name" text
);

-- Badge scans
create table scans (
  "id" serial primary key,
  "user_id" int references users,
  "badge_scan_time" timestamp
);

-- Work shifts
create table shifts (
  "id" serial primary key,
  "user_id" int references users,
  "scan_id_start" int references scans, -- clocking in
  "scan_id_end" int references scans, -- clocking out
  "attendance_status" text
);

In this case, you need to explicitly define the join because the joining column on shifts is ambiguous as they are both referencing the scans table.

To fetch all the shifts with scan_id_start and scan_id_end related to a specific scan, use the following syntax:

JavaScript

js
const { data, error } = await supabase.from('shifts').select(
  `
    *,
    start_scan:scans!scan_id_start (
      id,
      user_id,
      badge_scan_time
    ),
   end_scan:scans!scan_id_end (
     id,
     user_id,
     badge_scan_time
    )
  `
)
GraphQL

javascript
const Query = `
  query {
    shiftsCollection {
      edges {
        node {
          id
          user_id
          attendance_status
          scan_id_start {
            id
            user_id
            badge_scan_time
          }
          scan_id_end {
            id
            user_id
            badge_scan_time
          }
        }
      }
    }
  }
`