import GraphiQLIDE from '@site/src/components/GraphiQLIDE';

Postgres: Distinct Query Results

The distinct_on argument

You can fetch rows with only distinct values of a column using the distinct_on argument.

It is typically recommended to use order_by along with distinct_on to ensure we get predictable results (otherwise any arbitrary row with a distinct value of the column may be returned). Note that the distinct_on column needs to be the first column in the order_by expression. See sort queries for more info on using order_by.

employees (
  distinct_on: [employees_select_column]
  order_by: [employees_order_by]
): [employees]!

# select column enum type for "employees" table
enum employees_select_column {
  id
  name
  department
  salary
}

You can see the complete specification of the distinct_on argument in the API reference.

Fetch results with distinct values of a particular field

For example, fetch the employee with the highest salary from each department:

<GraphiQLIDE query={query { employees ( distinct_on: [department] order_by: [ {department: asc}, {salary: desc} ] ) { id name department salary } }} response={{ "data": { "employees": [ { "id": 5, "name": "Kamila", "department": "Engineering", "salary": 4325 }, { "id": 4, "name": "Damien", "department": "Product", "salary": 3124 }, { "id": 7, "name": "Rickard", "department": "Services", "salary": 2223 } ] } }} />