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90 lines
2.2 KiB
ReStructuredText
90 lines
2.2 KiB
ReStructuredText
.. meta::
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:description: Make distinct queries with Hasura
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:keywords: hasura, docs, query, distinct query
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.. _distinct_queries:
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Distinct query results
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======================
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.. contents:: Table of contents
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:backlinks: none
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:depth: 2
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:local:
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The **distinct_on** argument
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----------------------------
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You can fetch rows with only distinct values of a column using the ``distinct_on`` argument.
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It is typically recommended to use ``order_by`` along with ``distinct_on`` to ensure we get predictable results
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*(otherwise any arbitrary row with a distinct value of the column may be returned)*.
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Note that the ``distinct_on`` column needs to be the first column in the ``order_by`` expression.
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See :ref:`sort queries <sort_query_results>` for more info on using ``order_by``.
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.. code-block:: graphql
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employee (
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distinct_on: [employee_select_column]
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order_by: [employee_order_by]
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): [employee]!
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# select column enum type for "employee" table
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enum employee_select_column {
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id
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name
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department
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salary
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}
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You can see the complete specification of the ``distinct_on`` argument in the :ref:`API reference <DistinctOnExp>`.
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Fetch results with distinct values of a particular field
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--------------------------------------------------------
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**For example**, fetch the employee with the highest salary from each department:
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.. graphiql::
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:view_only:
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:query:
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query {
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employee (
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distinct_on: [department]
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order_by: [
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{department: asc},
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{salary: desc}
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]
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) {
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id
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name
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department
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salary
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}
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}
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:response:
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{
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"data": {
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"employee": [
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{
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"id": 5,
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"name": "Kamila",
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"department": "Engineering",
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"salary": 4325
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},
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{
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"id": 4,
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"name": "Damien",
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"department": "Product",
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"salary": 3124
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},
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{
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"id": 7,
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"name": "Rickard",
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"department": "Services",
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"salary": 2223
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}
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]
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}
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}
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