diff --git a/server/lib/api-tests/api-tests.cabal b/server/lib/api-tests/api-tests.cabal
index 53efa5c5721..deb21d49fbc 100644
--- a/server/lib/api-tests/api-tests.cabal
+++ b/server/lib/api-tests/api-tests.cabal
@@ -117,6 +117,7 @@ executable api-tests
     Test.Queries.Directives.IncludeSpec
     Test.Queries.Directives.SkipSpec
     Test.Queries.DirectivesSpec
+    Test.Queries.DistinctSpec
     Test.Queries.ExplainSpec
     Test.Queries.FilterSearchSpec
     Test.Queries.FragmentsSpec
diff --git a/server/lib/api-tests/test/Test/Queries/DistinctSpec.hs b/server/lib/api-tests/test/Test/Queries/DistinctSpec.hs
new file mode 100644
index 00000000000..a75b98e303d
--- /dev/null
+++ b/server/lib/api-tests/test/Test/Queries/DistinctSpec.hs
@@ -0,0 +1,167 @@
+{-# LANGUAGE QuasiQuotes #-}
+
+-- |
+-- Tests for @distinct@ queries.
+--
+-- https://hasura.io/docs/latest/queries/postgres/distinct-queries/
+module Test.Queries.DistinctSpec where
+
+import Data.Aeson (Value)
+import Data.List.NonEmpty qualified as NE
+import Harness.Backend.BigQuery qualified as BigQuery
+import Harness.Backend.Citus qualified as Citus
+import Harness.Backend.Postgres qualified as Postgres
+import Harness.GraphqlEngine (postGraphql)
+import Harness.Quoter.Graphql (graphql)
+import Harness.Quoter.Yaml (interpolateYaml)
+import Harness.Test.Fixture qualified as Fixture
+import Harness.Test.Schema (Table (..), table)
+import Harness.Test.Schema qualified as Schema
+import Harness.TestEnvironment (TestEnvironment)
+import Harness.Yaml (shouldReturnYaml)
+import Hasura.Prelude
+import Test.Hspec (SpecWith, it)
+
+spec :: SpecWith TestEnvironment
+spec = do
+  Fixture.run
+    ( NE.fromList
+        [ (Fixture.fixture $ Fixture.Backend Fixture.Postgres)
+            { Fixture.setupTeardown = \(testEnv, _) ->
+                [ Postgres.setupTablesAction schema testEnv
+                ]
+            },
+          (Fixture.fixture $ Fixture.Backend Fixture.Citus)
+            { Fixture.setupTeardown = \(testEnv, _) ->
+                [ Citus.setupTablesAction schema testEnv
+                ]
+            },
+          (Fixture.fixture $ Fixture.Backend Fixture.BigQuery)
+            { Fixture.setupTeardown = \(testEnv, _) ->
+                [ BigQuery.setupTablesAction schema testEnv
+                ],
+              Fixture.customOptions =
+                Just $
+                  Fixture.defaultOptions
+                    { Fixture.stringifyNumbers = True
+                    }
+            }
+        ]
+    )
+    tests
+
+--------------------------------------------------------------------------------
+-- Schema
+
+schema :: [Schema.Table]
+schema =
+  [ (table "author")
+      { tableColumns =
+          [ Schema.column "id" Schema.TInt,
+            Schema.column "name" Schema.TStr,
+            Schema.columnNull "genre" Schema.TStr,
+            Schema.column "age" Schema.TInt
+          ],
+        tablePrimaryKey = ["id"],
+        tableData =
+          [ [Schema.VInt 1, Schema.VStr "Alice", Schema.VStr "Action", Schema.VInt 25],
+            [Schema.VInt 2, Schema.VStr "Bob", Schema.VStr "Biography", Schema.VInt 40],
+            [Schema.VInt 3, Schema.VStr "Carol", Schema.VStr "Crime", Schema.VInt 35],
+            [Schema.VInt 4, Schema.VStr "Dave", Schema.VStr "Action", Schema.VInt 30],
+            [Schema.VInt 5, Schema.VStr "Eve", Schema.VStr "Crime", Schema.VInt 25],
+            [Schema.VInt 6, Schema.VStr "Bart", Schema.VNull, Schema.VInt 25]
+          ]
+      }
+  ]
+
+--------------------------------------------------------------------------------
+-- Tests
+
+-- We specify the nulls ordering because the behaviour is not consistent between
+-- postgres and cockroach.
+--
+-- For postgres and citus:
+--   - @asc_nulls_last@ is the behaviour of @asc@
+--   - @desc_nulls_first@ is the behaviour of @desc@
+--
+-- For cockroach, it's the opposite:
+--   - @asc_nulls_first@ is the behaviour of @asc@
+--   - @desc_nulls_last@ is the behaviour of @desc@
+tests :: Fixture.Options -> SpecWith TestEnvironment
+tests opts = do
+  let shouldBe :: IO Value -> Value -> IO ()
+      shouldBe = shouldReturnYaml opts
+
+  it "Find the oldest writer of each genre - nulls last" \testEnvironment -> do
+    let schemaName :: Schema.SchemaName
+        schemaName = Schema.getSchemaName testEnvironment
+
+        actual :: IO Value
+        actual =
+          postGraphql
+            testEnvironment
+            [graphql|
+              query {
+                #{schemaName}_author (
+                  distinct_on: [genre],
+                  order_by: [ { genre: asc_nulls_last }, { age: desc }, { id: asc } ]
+                ) {
+                  id
+                  name
+                }
+              }
+            |]
+
+        expected :: Value
+        expected =
+          [interpolateYaml|
+            data:
+              #{schemaName}_author:
+              - id: 4
+                name: Dave
+              - id: 2
+                name: Bob
+              - id: 3
+                name: Carol
+              - id: 6
+                name: Bart
+          |]
+
+    actual `shouldBe` expected
+
+  it "Find the oldest writer of each genre - nulls first" \testEnvironment -> do
+    let schemaName :: Schema.SchemaName
+        schemaName = Schema.getSchemaName testEnvironment
+
+        actual :: IO Value
+        actual =
+          postGraphql
+            testEnvironment
+            [graphql|
+              query {
+                #{schemaName}_author (
+                  distinct_on: [genre],
+                  order_by: [ { genre: asc_nulls_first }, { age: desc }, { id: asc } ]
+                ) {
+                  id
+                  name
+                }
+              }
+            |]
+
+        expected :: Value
+        expected =
+          [interpolateYaml|
+            data:
+              #{schemaName}_author:
+              - id: 6
+                name: Bart
+              - id: 4
+                name: Dave
+              - id: 2
+                name: Bob
+              - id: 3
+                name: Carol
+          |]
+
+    actual `shouldBe` expected
diff --git a/server/lib/test-harness/src/Harness/Backend/BigQuery.hs b/server/lib/test-harness/src/Harness/Backend/BigQuery.hs
index 7287cb5bb71..974836a613f 100644
--- a/server/lib/test-harness/src/Harness/Backend/BigQuery.hs
+++ b/server/lib/test-harness/src/Harness/Backend/BigQuery.hs
@@ -61,7 +61,13 @@ run_ :: HasCallStack => String -> IO ()
 run_ query = do
   void $
     runWithRetry
-      (\conn -> (Execute.executeBigQuery conn Execute.BigQuery {Execute.query = fromString query, Execute.parameters = mempty}))
+      ( \conn -> do
+          res <-
+            Execute.executeBigQuery
+              conn
+              Execute.BigQuery {Execute.query = fromString query, Execute.parameters = mempty}
+          onLeft res \x -> liftIO (bigQueryError x query)
+      )
 
 bigQueryError :: HasCallStack => Execute.ExecuteProblem -> String -> IO a
 bigQueryError e query =
@@ -85,7 +91,7 @@ removeDataset schemaName =
   void $ runWithRetry (\conn -> Execute.deleteDataset conn $ unSchemaName schemaName)
 
 -- | Serialize Table into a SQL statement, as needed, and execute it on the BigQuery backend
-createTable :: SchemaName -> Schema.Table -> IO ()
+createTable :: HasCallStack => SchemaName -> Schema.Table -> IO ()
 createTable schemaName table@Schema.Table {tableName, tableColumns} = do
   run_ $
     T.unpack $
@@ -149,7 +155,7 @@ serialize = \case
   VCustomValue bsv -> Schema.formatBackendScalarValueType $ Schema.backendScalarValue bsv bsvBigQuery
 
 -- | Serialize Table into an SQL DROP statement and execute it
-dropTable :: SchemaName -> Schema.Table -> IO ()
+dropTable :: HasCallStack => SchemaName -> Schema.Table -> IO ()
 dropTable schemaName Schema.Table {tableName} = do
   run_ $
     T.unpack $
@@ -193,7 +199,7 @@ untrackTable testEnvironment schemaName Schema.Table {tableName} = do
 
 -- | Setup the schema in the most expected way.
 -- NOTE: Certain test modules may warrant having their own local version.
-setup :: [Schema.Table] -> (TestEnvironment, ()) -> IO ()
+setup :: HasCallStack => [Schema.Table] -> (TestEnvironment, ()) -> IO ()
 setup tables' (testEnvironment, _) = do
   let source = defaultSource BigQuery
       backendType = defaultBackendTypeString BigQuery
@@ -249,24 +255,24 @@ teardown (reverse -> tables) (testEnvironment, _) = do
     -- remove test dataset
     (removeDataset schemaName)
 
-setupTablesAction :: [Schema.Table] -> TestEnvironment -> SetupAction
+setupTablesAction :: HasCallStack => [Schema.Table] -> TestEnvironment -> SetupAction
 setupTablesAction ts env =
   SetupAction
     (setup ts (env, ()))
     (const $ teardown ts (env, ()))
 
-setupPermissionsAction :: [Permissions.Permission] -> TestEnvironment -> SetupAction
+setupPermissionsAction :: HasCallStack => [Permissions.Permission] -> TestEnvironment -> SetupAction
 setupPermissionsAction permissions env =
   SetupAction
     (setupPermissions permissions env)
     (const $ teardownPermissions permissions env)
 
 -- | Setup the given permissions to the graphql engine in a TestEnvironment.
-setupPermissions :: [Permissions.Permission] -> TestEnvironment -> IO ()
+setupPermissions :: HasCallStack => [Permissions.Permission] -> TestEnvironment -> IO ()
 setupPermissions permissions env = Permissions.setup BigQuery permissions env
 
 -- | Remove the given permissions from the graphql engine in a TestEnvironment.
-teardownPermissions :: [Permissions.Permission] -> TestEnvironment -> IO ()
+teardownPermissions :: HasCallStack => [Permissions.Permission] -> TestEnvironment -> IO ()
 teardownPermissions permissions env = Permissions.teardown BigQuery permissions env
 
 -- | We get @jobRateLimitExceeded@ errors from BigQuery if we run too many DML operations in short intervals.