diff --git a/integration_test/myxql/test_helper.exs b/integration_test/myxql/test_helper.exs
index e9b6a29e..fb966982 100644
--- a/integration_test/myxql/test_helper.exs
+++ b/integration_test/myxql/test_helper.exs
@@ -113,7 +113,9 @@ excludes = [
   # MySQL doesn't support indexed parameters
   :placeholders,
   # MySQL doesn't support specifying columns for ON DELETE SET NULL
-  :on_delete_nilify_column_list
+  :on_delete_nilify_column_list,
+  # MySQL doesnt' support anything except a single column in DISTINCT
+  :multicolumn_distinct
 ]
 
 if Version.match?(version, ">= 8.0.0") do
diff --git a/integration_test/sql/subquery.exs b/integration_test/sql/subquery.exs
index 025086cb..d820924b 100644
--- a/integration_test/sql/subquery.exs
+++ b/integration_test/sql/subquery.exs
@@ -112,4 +112,42 @@ defmodule Ecto.Integration.SubQueryTest do
               select: fragment("? + ?", p.visits, ^1)
     assert [12, 12] = TestRepo.all(query)
   end
+
+  @tag :subquery_in_order_by
+  test "subqueries in order by" do
+    TestRepo.insert!(%Post{visits: 10, title: "hello"})
+    TestRepo.insert!(%Post{visits: 11, title: "hello"})
+
+    query = from p in Post, as: :p, order_by: [asc: exists(from p in Post, where: p.visits > parent_as(:p).visits)]
+
+    assert [%{visits: 11}, %{visits: 10}] = TestRepo.all(query)
+  end
+
+  @tag :multicolumn_distinct
+  @tag :subquery_in_distinct
+  test "subqueries in distinct" do
+    TestRepo.insert!(%Post{visits: 10, title: "hello1"})
+    TestRepo.insert!(%Post{visits: 10, title: "hello2"})
+    TestRepo.insert!(%Post{visits: 11, title: "hello"})
+
+    query = from p in Post, as: :p, distinct: exists(from p in Post, where: p.visits > parent_as(:p).visits), order_by: [asc: :title]
+
+    assert [%{title: "hello"}, %{title: "hello1"}] = TestRepo.all(query)
+  end
+
+  @tag :subquery_in_group_by
+  test "subqueries in group by" do
+    TestRepo.insert!(%Post{visits: 10, title: "hello1"})
+    TestRepo.insert!(%Post{visits: 10, title: "hello2"})
+    TestRepo.insert!(%Post{visits: 11, title: "hello"})
+
+    query = from p in Post, as: :p, select: sum(p.visits), group_by: exists(from p in Post, where: p.visits > parent_as(:p).visits), order_by: [sum(p.visits)]
+
+    query
+    |> TestRepo.all()
+    |> Enum.map(&Decimal.new/1)
+    |> Enum.zip([Decimal.new(11), Decimal.new(20)])
+    |> Enum.all?(fn {a, b} -> Decimal.eq?(a, b) end)
+    |> assert()
+  end
 end
diff --git a/integration_test/tds/test_helper.exs b/integration_test/tds/test_helper.exs
index 89e2d13d..9e0788b6 100644
--- a/integration_test/tds/test_helper.exs
+++ b/integration_test/tds/test_helper.exs
@@ -57,7 +57,13 @@ ExUnit.start(
     # MSSQL can't reference aliased columns in ORDER BY expressions
     :selected_as_with_order_by_expression,
     # MSSQL doesn't support specifying columns for ON DELETE SET NULL
-    :on_delete_nilify_column_list
+    :on_delete_nilify_column_list,
+    # MSSQL doesnt' support anything except a single column in DISTINCT
+    :multicolumn_distinct,
+    # MSSQL doesnt' support subqueries in group by or in distinct
+    :subquery_in_group_by,
+    :subquery_in_distinct,
+    :subquery_in_order_by
   ]
 )
 
diff --git a/lib/ecto/adapters/myxql/connection.ex b/lib/ecto/adapters/myxql/connection.ex
index 61ca8952..fb363b87 100644
--- a/lib/ecto/adapters/myxql/connection.ex
+++ b/lib/ecto/adapters/myxql/connection.ex
@@ -75,7 +75,7 @@ if Code.ensure_loaded?(MyXQL) do
     ## Query
 
     @parent_as __MODULE__
-    alias Ecto.Query.{BooleanExpr, JoinExpr, QueryExpr, WithExpr}
+    alias Ecto.Query.{BooleanExpr, ByExpr, JoinExpr, QueryExpr, WithExpr}
 
     @impl true
     def all(query, as_prefix \\ []) do
@@ -319,10 +319,10 @@ if Code.ensure_loaded?(MyXQL) do
     end
 
     defp distinct(nil, _sources, _query), do: []
-    defp distinct(%QueryExpr{expr: true}, _sources, _query), do: "DISTINCT "
-    defp distinct(%QueryExpr{expr: false}, _sources, _query), do: []
+    defp distinct(%ByExpr{expr: true}, _sources, _query), do: "DISTINCT "
+    defp distinct(%ByExpr{expr: false}, _sources, _query), do: []
 
-    defp distinct(%QueryExpr{expr: exprs}, _sources, query) when is_list(exprs) do
+    defp distinct(%ByExpr{expr: exprs}, _sources, query) when is_list(exprs) do
       error!(query, "DISTINCT with multiple columns is not supported by MySQL")
     end
 
@@ -511,8 +511,8 @@ if Code.ensure_loaded?(MyXQL) do
     defp group_by(%{group_bys: group_bys} = query, sources) do
       [
         " GROUP BY "
-        | Enum.map_intersperse(group_bys, ", ", fn %QueryExpr{expr: expr} ->
-            Enum.map_intersperse(expr, ", ", &expr(&1, sources, query))
+        | Enum.map_intersperse(group_bys, ", ", fn %ByExpr{expr: expr} ->
+            Enum.map_intersperse(expr, ", ", &top_level_expr(&1, sources, query))
           end)
       ]
     end
@@ -549,14 +549,14 @@ if Code.ensure_loaded?(MyXQL) do
     defp order_by(%{order_bys: order_bys} = query, sources) do
       [
         " ORDER BY "
-        | Enum.map_intersperse(order_bys, ", ", fn %QueryExpr{expr: expr} ->
+        | Enum.map_intersperse(order_bys, ", ", fn %ByExpr{expr: expr} ->
             Enum.map_intersperse(expr, ", ", &order_by_expr(&1, sources, query))
           end)
       ]
     end
 
     defp order_by_expr({dir, expr}, sources, query) do
-      str = expr(expr, sources, query)
+      str = top_level_expr(expr, sources, query)
 
       case dir do
         :asc -> str
@@ -627,6 +627,21 @@ if Code.ensure_loaded?(MyXQL) do
       [?(, expr(expr, sources, query), ?)]
     end
 
+    defp top_level_expr(%Ecto.SubQuery{query: query}, sources, parent_query) do
+      combinations =
+        Enum.map(query.combinations, fn {type, combination_query} ->
+          {type, put_in(combination_query.aliases[@parent_as], {parent_query, sources})}
+        end)
+
+      query = put_in(query.combinations, combinations)
+      query = put_in(query.aliases[@parent_as], {parent_query, sources})
+      [all(query, subquery_as_prefix(sources))]
+    end
+
+    defp top_level_expr(other, sources, parent_query) do
+      expr(other, sources, parent_query)
+    end
+
     defp expr({:^, [], [_ix]}, _sources, _query) do
       ~c"?"
     end
@@ -687,15 +702,8 @@ if Code.ensure_loaded?(MyXQL) do
       error!(query, "MySQL adapter does not support aggregate filters")
     end
 
-    defp expr(%Ecto.SubQuery{query: query}, sources, parent_query) do
-      combinations =
-        Enum.map(query.combinations, fn {type, combination_query} ->
-          {type, put_in(combination_query.aliases[@parent_as], {parent_query, sources})}
-        end)
-
-      query = put_in(query.combinations, combinations)
-      query = put_in(query.aliases[@parent_as], {parent_query, sources})
-      [?(, all(query, subquery_as_prefix(sources)), ?)]
+    defp expr(%Ecto.SubQuery{} = subquery, sources, parent_query) do
+      [?(, top_level_expr(subquery, sources, parent_query), ?)]
     end
 
     defp expr({:fragment, _, [kw]}, _sources, query) when is_list(kw) or tuple_size(kw) == 3 do
@@ -790,7 +798,13 @@ if Code.ensure_loaded?(MyXQL) do
           [op_to_binary(left, sources, query), op | op_to_binary(right, sources, query)]
 
         {:fun, fun} ->
-          [fun, ?(, modifier, Enum.map_intersperse(args, ", ", &expr(&1, sources, query)), ?)]
+          [
+            fun,
+            ?(,
+            modifier,
+            Enum.map_intersperse(args, ", ", &top_level_expr(&1, sources, query)),
+            ?)
+          ]
       end
     end
 
diff --git a/lib/ecto/adapters/postgres/connection.ex b/lib/ecto/adapters/postgres/connection.ex
index f0ed9670..9b59e7f5 100644
--- a/lib/ecto/adapters/postgres/connection.ex
+++ b/lib/ecto/adapters/postgres/connection.ex
@@ -155,7 +155,7 @@ if Code.ensure_loaded?(Postgrex) do
     end
 
     @parent_as __MODULE__
-    alias Ecto.Query.{BooleanExpr, JoinExpr, QueryExpr, WithExpr}
+    alias Ecto.Query.{BooleanExpr, ByExpr, JoinExpr, QueryExpr, WithExpr}
 
     @impl true
     def all(query, as_prefix \\ []) do
@@ -551,11 +551,11 @@ if Code.ensure_loaded?(Postgrex) do
     end
 
     defp distinct(nil, _, _), do: {[], []}
-    defp distinct(%QueryExpr{expr: []}, _, _), do: {[], []}
-    defp distinct(%QueryExpr{expr: true}, _, _), do: {" DISTINCT", []}
-    defp distinct(%QueryExpr{expr: false}, _, _), do: {[], []}
+    defp distinct(%ByExpr{expr: []}, _, _), do: {[], []}
+    defp distinct(%ByExpr{expr: true}, _, _), do: {" DISTINCT", []}
+    defp distinct(%ByExpr{expr: false}, _, _), do: {[], []}
 
-    defp distinct(%QueryExpr{expr: exprs}, sources, query) do
+    defp distinct(%ByExpr{expr: exprs}, sources, query) do
       {[
          " DISTINCT ON (",
          Enum.map_intersperse(exprs, ", ", fn {_, expr} -> expr(expr, sources, query) end),
@@ -772,7 +772,7 @@ if Code.ensure_loaded?(Postgrex) do
       [
         " GROUP BY "
         | Enum.map_intersperse(group_bys, ", ", fn
-            %QueryExpr{expr: expr} ->
+            %ByExpr{expr: expr} ->
               Enum.map_intersperse(expr, ", ", &expr(&1, sources, query))
           end)
       ]
diff --git a/lib/ecto/adapters/tds/connection.ex b/lib/ecto/adapters/tds/connection.ex
index 763cb090..c0669e92 100644
--- a/lib/ecto/adapters/tds/connection.ex
+++ b/lib/ecto/adapters/tds/connection.ex
@@ -149,7 +149,7 @@ if Code.ensure_loaded?(Tds) do
 
     @parent_as __MODULE__
     alias Ecto.Query
-    alias Ecto.Query.{BooleanExpr, JoinExpr, QueryExpr, WithExpr}
+    alias Ecto.Query.{BooleanExpr, ByExpr, JoinExpr, QueryExpr, WithExpr}
 
     @impl true
     def all(query, as_prefix \\ []) do
@@ -390,10 +390,10 @@ if Code.ensure_loaded?(Tds) do
     end
 
     defp distinct(nil, _sources, _query), do: []
-    defp distinct(%QueryExpr{expr: true}, _sources, _query), do: "DISTINCT "
-    defp distinct(%QueryExpr{expr: false}, _sources, _query), do: []
+    defp distinct(%ByExpr{expr: true}, _sources, _query), do: "DISTINCT "
+    defp distinct(%ByExpr{expr: false}, _sources, _query), do: []
 
-    defp distinct(%QueryExpr{expr: exprs}, _sources, query) when is_list(exprs) do
+    defp distinct(%ByExpr{expr: exprs}, _sources, query) when is_list(exprs) do
       error!(
         query,
         "DISTINCT with multiple columns is not supported by MsSQL. " <>
@@ -584,8 +584,8 @@ if Code.ensure_loaded?(Tds) do
     defp group_by(%{group_bys: group_bys} = query, sources) do
       [
         " GROUP BY "
-        | Enum.map_intersperse(group_bys, ", ", fn %QueryExpr{expr: expr} ->
-            Enum.map_intersperse(expr, ", ", &expr(&1, sources, query))
+        | Enum.map_intersperse(group_bys, ", ", fn %ByExpr{expr: expr} ->
+            Enum.map_intersperse(expr, ", ", &top_level_expr(&1, sources, query))
           end)
       ]
     end
@@ -595,14 +595,14 @@ if Code.ensure_loaded?(Tds) do
     defp order_by(%{order_bys: order_bys} = query, sources) do
       [
         " ORDER BY "
-        | Enum.map_intersperse(order_bys, ", ", fn %QueryExpr{expr: expr} ->
+        | Enum.map_intersperse(order_bys, ", ", fn %ByExpr{expr: expr} ->
             Enum.map_intersperse(expr, ", ", &order_by_expr(&1, sources, query))
           end)
       ]
     end
 
     defp order_by_expr({dir, expr}, sources, query) do
-      str = expr(expr, sources, query)
+      str = top_level_expr(expr, sources, query)
 
       case dir do
         :asc -> str
@@ -708,6 +708,21 @@ if Code.ensure_loaded?(Tds) do
       [?(, expr(expr, sources, query), ?)]
     end
 
+    defp top_level_expr(%Ecto.SubQuery{query: query}, sources, parent_query) do
+      combinations =
+        Enum.map(query.combinations, fn {type, combination_query} ->
+          {type, put_in(combination_query.aliases[@parent_as], {parent_query, sources})}
+        end)
+
+      query = put_in(query.combinations, combinations)
+      query = put_in(query.aliases[@parent_as], {parent_query, sources})
+      [all(query, subquery_as_prefix(sources))]
+    end
+
+    defp top_level_expr(other, sources, parent_query) do
+      expr(other, sources, parent_query)
+    end
+
     # :^ - represents parameter ix is index number
     defp expr({:^, [], [idx]}, _sources, _query) do
       "@#{idx + 1}"
@@ -787,15 +802,8 @@ if Code.ensure_loaded?(Tds) do
       error!(query, "Tds adapter does not support aggregate filters")
     end
 
-    defp expr(%Ecto.SubQuery{query: query}, sources, parent_query) do
-      combinations =
-        Enum.map(query.combinations, fn {type, combination_query} ->
-          {type, put_in(combination_query.aliases[@parent_as], {parent_query, sources})}
-        end)
-
-      query = put_in(query.combinations, combinations)
-      query = put_in(query.aliases[@parent_as], {parent_query, sources})
-      [?(, all(query, subquery_as_prefix(sources)), ?)]
+    defp expr(%Ecto.SubQuery{} = subquery, sources, parent_query) do
+      [?(, top_level_expr(subquery, sources, parent_query), ?)]
     end
 
     defp expr({:fragment, _, [kw]}, _sources, query) when is_list(kw) or tuple_size(kw) == 3 do
@@ -873,7 +881,13 @@ if Code.ensure_loaded?(Tds) do
           [op_to_binary(left, sources, query), op | op_to_binary(right, sources, query)]
 
         {:fun, fun} ->
-          [fun, ?(, modifier, Enum.map_intersperse(args, ", ", &expr(&1, sources, query)), ?)]
+          [
+            fun,
+            ?(,
+            modifier,
+            Enum.map_intersperse(args, ", ", &top_level_expr(&1, sources, query)),
+            ?)
+          ]
       end
     end
 
diff --git a/mix.lock b/mix.lock
index b04443eb..3d059342 100644
--- a/mix.lock
+++ b/mix.lock
@@ -4,8 +4,8 @@
   "decimal": {:hex, :decimal, "2.1.1", "5611dca5d4b2c3dd497dec8f68751f1f1a54755e8ed2a966c2633cf885973ad6", [:mix], [], "hexpm", "53cfe5f497ed0e7771ae1a475575603d77425099ba5faef9394932b35020ffcc"},
   "deep_merge": {:hex, :deep_merge, "1.0.0", "b4aa1a0d1acac393bdf38b2291af38cb1d4a52806cf7a4906f718e1feb5ee961", [:mix], [], "hexpm", "ce708e5f094b9cd4e8f2be4f00d2f4250c4095be93f8cd6d018c753894885430"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.39", "424642f8335b05bb9eb611aa1564c148a8ee35c9c8a8bba6e129d51a3e3c6769", [:mix], [], "hexpm", "06553a88d1f1846da9ef066b87b57c6f605552cfbe40d20bd8d59cc6bde41944"},
-  "ecto": {:git, "https://github.com/elixir-ecto/ecto.git", "bed81b9a69f3425147fb57df1b3dd5fb4c95792c", []},
-  "ex_doc": {:hex, :ex_doc, "0.32.2", "f60bbeb6ccbe75d005763e2a328e6f05e0624232f2393bc693611c2d3ae9fa0e", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "a4480305cdfe7fdfcbb77d1092c76161626d9a7aa4fb698aee745996e34602df"},
+  "ecto": {:git, "https://github.com/elixir-ecto/ecto.git", "a898915d2f16dbf1257b8c83a11a1ae07193de42", []},
+  "ex_doc": {:hex, :ex_doc, "0.33.0", "690562b153153c7e4d455dc21dab86e445f66ceba718defe64b0ef6f0bd83ba0", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "3f69adc28274cb51be37d09b03e4565232862a4b10288a3894587b0131412124"},
   "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
   "makeup": {:hex, :makeup, "1.1.2", "9ba8837913bdf757787e71c1581c21f9d2455f4dd04cfca785c70bbfff1a76a3", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "cce1566b81fbcbd21eca8ffe808f33b221f9eee2cbc7a1706fc3da9ff18e6cac"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.16.2", "627e84b8e8bf22e60a2579dad15067c755531fea049ae26ef1020cad58fe9578", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "41193978704763f6bbe6cc2758b84909e62984c7752b3784bd3c218bb341706b"},
diff --git a/test/ecto/adapters/myxql_test.exs b/test/ecto/adapters/myxql_test.exs
index a6a1bf99..4baac56d 100644
--- a/test/ecto/adapters/myxql_test.exs
+++ b/test/ecto/adapters/myxql_test.exs
@@ -392,6 +392,23 @@ defmodule Ecto.Adapters.MyXQLTest do
 
                    all(query)
                  end
+
+    assert_raise Ecto.QueryError,
+                 ~r"DISTINCT with multiple columns is not supported by MySQL",
+                 fn ->
+                   query =
+                     from(row in Schema, as: :r, select: row.x)
+                     |> distinct(
+                       exists(
+                         from other_schema in "schema",
+                           where: other_schema.x == parent_as(:r).x,
+                           select: [other_schema.x]
+                       )
+                     )
+                     |> plan()
+
+                   all(query)
+                 end
   end
 
   test "coalesce" do
@@ -446,6 +463,22 @@ defmodule Ecto.Adapters.MyXQLTest do
         Schema |> order_by([r], [{^dir, r.x}]) |> select([r], r.x) |> plan() |> all()
       end
     end
+
+    query =
+      from(row in Schema, as: :r)
+      |> order_by(
+        asc:
+          exists(
+            from other_schema in "schema",
+              where: other_schema.x == parent_as(:r).x,
+              select: [other_schema.x]
+          )
+      )
+      |> select([r], r.x)
+      |> plan()
+
+    assert all(query) ==
+             ~s{SELECT s0.`x` FROM `schema` AS s0 ORDER BY exists(SELECT ss0.`x` AS `result` FROM `schema` AS ss0 WHERE (ss0.`x` = s0.`x`))}
   end
 
   test "union and union all" do
@@ -835,6 +868,21 @@ defmodule Ecto.Adapters.MyXQLTest do
 
     query = Schema |> group_by([r], []) |> select([r], r.x) |> plan()
     assert all(query) == ~s{SELECT s0.`x` FROM `schema` AS s0}
+
+    query =
+      from(row in Schema, as: :r, select: row.x)
+      |> group_by(
+        [r],
+        exists(
+          from other_schema in "schema",
+            where: other_schema.x == parent_as(:r).x,
+            select: [other_schema.x]
+        )
+      )
+      |> plan()
+
+    assert all(query) ==
+             ~s{SELECT s0.`x` FROM `schema` AS s0 GROUP BY exists(SELECT ss0.`x` AS `result` FROM `schema` AS ss0 WHERE (ss0.`x` = s0.`x`))}
   end
 
   test "interpolated values" do
@@ -1024,6 +1072,26 @@ defmodule Ecto.Adapters.MyXQLTest do
                ~s{SELECT s0.`x` FROM `schema` AS s0 WINDOW `w` AS (PARTITION BY s0.`x`)}
     end
 
+    test "window with subquery" do
+      query =
+        from(row in Schema, as: :r)
+        |> select([r], r.x)
+        |> windows([r],
+          w: [
+            order_by:
+              exists(
+                from other_schema in "schema",
+                  where: other_schema.x == parent_as(:r).x,
+                  select: [other_schema.x]
+              )
+          ]
+        )
+        |> plan
+
+      assert all(query) ==
+               ~s{SELECT s0.`x` FROM `schema` AS s0 WINDOW `w` AS (ORDER BY exists(SELECT ss0.`x` AS `result` FROM `schema` AS ss0 WHERE (ss0.`x` = s0.`x`)))}
+    end
+
     test "two windows" do
       query =
         Schema
diff --git a/test/ecto/adapters/postgres_test.exs b/test/ecto/adapters/postgres_test.exs
index 62915efb..a5f358f2 100644
--- a/test/ecto/adapters/postgres_test.exs
+++ b/test/ecto/adapters/postgres_test.exs
@@ -530,6 +530,20 @@ defmodule Ecto.Adapters.PostgresTest do
 
     query = Schema |> distinct(false) |> select([r], {r.x, r.y}) |> plan()
     assert all(query) == ~s{SELECT s0."x", s0."y" FROM "schema" AS s0}
+
+    query =
+      from(row in Schema, as: :r, select: row.x)
+      |> distinct(
+        exists(
+          from other_schema in "schema",
+            where: other_schema.x == parent_as(:r).x,
+            select: [other_schema.x]
+        )
+      )
+      |> plan()
+
+    assert all(query) ==
+             ~s{SELECT DISTINCT ON (exists((SELECT ss0."x" AS "result" FROM "schema" AS ss0 WHERE (ss0."x" = s0."x")))) s0."x" FROM "schema" AS s0}
   end
 
   test "distinct with order by" do
@@ -618,6 +632,22 @@ defmodule Ecto.Adapters.PostgresTest do
     assert all(query) ==
              ~s{SELECT s0."x" FROM "schema" AS s0 ORDER BY s0."x" ASC NULLS FIRST, s0."y" DESC NULLS FIRST}
 
+    query =
+      from(row in Schema, as: :r)
+      |> order_by(
+        asc:
+          exists(
+            from other_schema in "schema",
+              where: other_schema.x == parent_as(:r).x,
+              select: [other_schema.x]
+          )
+      )
+      |> select([r], r.x)
+      |> plan()
+
+    assert all(query) ==
+             ~s{SELECT s0."x" FROM "schema" AS s0 ORDER BY exists((SELECT ss0."x" AS "result" FROM "schema" AS ss0 WHERE (ss0."x" = s0."x")))}
+
     query =
       Schema
       |> order_by([r], asc_nulls_last: r.x, desc_nulls_last: r.y)
@@ -1057,6 +1087,21 @@ defmodule Ecto.Adapters.PostgresTest do
 
     query = Schema |> group_by([r], []) |> select([r], r.x) |> plan()
     assert all(query) == ~s{SELECT s0."x" FROM "schema" AS s0}
+
+    query =
+      from(row in Schema, as: :r, select: row.x)
+      |> group_by(
+        [r],
+        exists(
+          from other_schema in "schema",
+            where: other_schema.x == parent_as(:r).x,
+            select: [other_schema.x]
+        )
+      )
+      |> plan()
+
+    assert all(query) ==
+             ~s{SELECT s0."x" FROM "schema" AS s0 GROUP BY exists((SELECT ss0."x" AS "result" FROM "schema" AS ss0 WHERE (ss0."x" = s0."x")))}
   end
 
   test "arrays and sigils" do
@@ -1364,6 +1409,26 @@ defmodule Ecto.Adapters.PostgresTest do
                ~s{SELECT s0."x" FROM "schema" AS s0 WINDOW "w" AS (PARTITION BY s0."x")}
     end
 
+    test "window with subquery" do
+      query =
+        from(row in Schema, as: :r)
+        |> select([r], r.x)
+        |> windows([r],
+          w: [
+            order_by:
+              exists(
+                from other_schema in "schema",
+                  where: other_schema.x == parent_as(:r).x,
+                  select: [other_schema.x]
+              )
+          ]
+        )
+        |> plan
+
+      assert all(query) ==
+               ~s{SELECT s0."x" FROM "schema" AS s0 WINDOW "w" AS (ORDER BY exists((SELECT ss0."x" AS "result" FROM "schema" AS ss0 WHERE (ss0."x" = s0."x"))))}
+    end
+
     test "two windows" do
       query =
         Schema
diff --git a/test/ecto/adapters/tds_test.exs b/test/ecto/adapters/tds_test.exs
index dda71040..1b5f9ac8 100644
--- a/test/ecto/adapters/tds_test.exs
+++ b/test/ecto/adapters/tds_test.exs
@@ -463,6 +463,23 @@ defmodule Ecto.Adapters.TdsTest do
 
                    all(query)
                  end
+
+    assert_raise Ecto.QueryError,
+                 ~r"DISTINCT with multiple columns is not supported by MsSQL",
+                 fn ->
+                   query =
+                     from(row in Schema, as: :r, select: row.x)
+                     |> distinct(
+                       exists(
+                         from other_schema in "schema",
+                           where: other_schema.x == parent_as(:r).x,
+                           select: [other_schema.x]
+                       )
+                     )
+                     |> plan()
+
+                   all(query)
+                 end
   end
 
   test "select with operation" do