Simple Joins

Sometimes, you would want to fetch data from multiple tables using a single query. In these situations, you should create a view by joining the tables and query the view for the combined data.

Let’s take a simple example where we have two tables student and student_batch_info.

Table Columns
student student_id, name
student_batch_info student_id, batch_id, teacher_name, class_name

As you can see above, both the tables have student_id as a common column. Now let’s create a view to join all of this data:

CREATE VIEW student_info_all AS
  SELECT s.student_id, s.name, sbi.teacher_name, sbi.class_name
  From student s, student_batch_info sbi
  WHERE s.student_id = sbi.student_id;

Head to Data > SQL section of the API console and run the above SQL command. Ensure that you check the Track Table checkbox before running the query so that you can use Data APIs to query the view.

Query the data

GraphQL
JSON API
query {
  student_info_all {
    student_id
    name
    teacher_name
    class_name
  }
}

POST data.<cluster-name>.hasura-app.io/v1/query HTTP/1.1
Content-Type: application/json
Authorization: Bearer <auth-token> # optional if cookie is set
X-Hasura-Role: <role>  # optional. Pass if only specific user role has access

{
 "type": "select",
 "args": {
     "table": "student_extra_info",
     "columns": [
         "student_id",
         "name",
         "teacher_name",
         "class_name"
     ]
 }
}
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