diff --git a/integration_test/sql/logging.exs b/integration_test/sql/logging.exs
index 0f92e9a7f..e0750bb1d 100644
--- a/integration_test/sql/logging.exs
+++ b/integration_test/sql/logging.exs
@@ -178,6 +178,74 @@ defmodule Ecto.Integration.LoggingTest do
     end
   end
 
+  describe ":comments option" do
+    test "comments query operations" do
+      assert capture_log(fn ->
+               TestRepo.all(Post, comments: [pre: "list_posts_q"], log: :error)
+             end) =~ "/* list_posts_q */ SELECT"
+
+      assert capture_log(fn ->
+               TestRepo.update_all(Post, [set: [visits: 0]], comments: [pre: "reset_visits_q"], log: :error)
+             end) =~ "/* reset_visits_q */ UPDATE"
+
+      assert capture_log(fn ->
+               TestRepo.delete_all(Post, comments: [pre: "purge_posts_q"], log: :error)
+             end) =~ "/* purge_posts_q */ DELETE"
+    end
+
+    test "supports both :pre and :post" do
+      assert capture_log(fn ->
+               TestRepo.all(Post, comments: [pre: "before_q", post: "after_q"], log: :error)
+             end) =~ ~r{/\* before_q \*/ SELECT.* /\* after_q \*/}
+    end
+
+    test "dynamic comments render and skip the query cache by default" do
+      assert capture_log(fn ->
+               TestRepo.all(Post, comments: [pre: "dyn_#{System.unique_integer()}"], log: :error)
+             end) =~ ~r{/\* dyn_-?\d+ \*/ SELECT}
+    end
+
+    test "query_cache: true opts back into caching for static comments" do
+      assert capture_log(fn ->
+               TestRepo.all(Post, comments: [pre: "static_q"], query_cache: true, log: :error)
+             end) =~ "/* static_q */ SELECT"
+    end
+
+    test "comments insert/update/delete/insert_all" do
+      assert capture_log(fn ->
+               TestRepo.insert!(%Post{title: "1"}, comments: [pre: "insert_create_post_q"], log: :error)
+             end) =~ "/* insert_create_post_q */ INSERT INTO"
+
+      post = TestRepo.insert!(%Post{title: "x"})
+
+      assert capture_log(fn ->
+               post
+               |> Ecto.Changeset.change(title: "y")
+               |> TestRepo.update!(comments: [pre: "update_post_q"], log: :error)
+             end) =~ "/* update_post_q */ UPDATE"
+
+      assert capture_log(fn ->
+               TestRepo.delete!(post, comments: [pre: "delete_post_q"], log: :error)
+             end) =~ "/* delete_post_q */ DELETE"
+
+      assert capture_log(fn ->
+               TestRepo.insert_all(Post, [%{title: "a"}], comments: [pre: "bulk_insert_posts_q"], log: :error)
+             end) =~ "/* bulk_insert_posts_q */ INSERT INTO"
+    end
+
+    test "rejects a comment that could break out of the comment block" do
+      assert_raise ArgumentError, ~r/cannot contain/, fn ->
+        TestRepo.insert!(%Post{title: "1"}, comments: [pre: "evil */ DROP TABLE posts"])
+      end
+    end
+
+    test "rejects a comment that MySQL/MariaDB would treat as executable" do
+      assert_raise ArgumentError, ~r/cannot start with/, fn ->
+        TestRepo.insert!(%Post{title: "1"}, comments: [pre: "!40000 DROP TABLE posts"])
+      end
+    end
+  end
+
   describe "parameter logging" do
     @describetag :parameter_logging
 
diff --git a/lib/ecto/adapters/myxql.ex b/lib/ecto/adapters/myxql.ex
index 6026cb260..fe8359889 100644
--- a/lib/ecto/adapters/myxql.ex
+++ b/lib/ecto/adapters/myxql.ex
@@ -373,12 +373,10 @@ defmodule Ecto.Adapters.MyXQL do
     insert_opts = if opts[:insert_mode], do: [insert_mode: opts[:insert_mode]], else: []
     sql = @conn.insert(prefix, source, fields, [fields], on_conflict, [], [], insert_opts)
 
-    opts =
-      if is_nil(Keyword.get(opts, :cache_statement)) do
-        [{:cache_statement, "ecto_insert_#{source}_#{length(fields)}"} | opts]
-      else
-        opts
-      end
+    # This adapter overrides insert/6 instead of going through
+    # Ecto.Adapters.SQL.struct/10, so wrap the `:comments` here too.
+    opts = Ecto.Adapters.SQL.put_default_cache_statement(opts, "ecto_insert_#{source}_#{length(fields)}")
+    sql = Ecto.Adapters.SQL.wrap_comments(sql, opts)
 
     case Ecto.Adapters.SQL.query(adapter_meta, sql, values ++ query_params, opts) do
       {:ok, %{num_rows: 0}} ->
diff --git a/lib/ecto/adapters/myxql/connection.ex b/lib/ecto/adapters/myxql/connection.ex
index 1823a9d3a..55a0e2efa 100644
--- a/lib/ecto/adapters/myxql/connection.ex
+++ b/lib/ecto/adapters/myxql/connection.ex
@@ -124,8 +124,10 @@ if Code.ensure_loaded?(MyXQL) do
       limit = limit(query, sources)
       offset = offset(query, sources)
       lock = lock(query, sources)
+      {pre_comments, post_comments} = SQL.comments(query.comments)
 
       [
+        pre_comments,
         cte,
         select,
         from,
@@ -137,7 +139,8 @@ if Code.ensure_loaded?(MyXQL) do
         combinations,
         order_by,
         limit,
-        offset | lock
+        offset,
+        lock | post_comments
       ]
     end
 
@@ -151,6 +154,7 @@ if Code.ensure_loaded?(MyXQL) do
 
       sources = create_names(query, [])
       cte = cte(query, sources)
+      {pre_comments, post_comments} = SQL.comments(query.comments)
       {from, name} = get_source(query, sources, 0, source)
 
       fields =
@@ -164,7 +168,7 @@ if Code.ensure_loaded?(MyXQL) do
       prefix = prefix || ["UPDATE ", from, " AS ", name, join, " SET "]
       where = where(%{query | wheres: wheres ++ query.wheres}, sources)
 
-      [cte, prefix, fields | where]
+      [pre_comments, cte, prefix, fields, where | post_comments]
     end
 
     @impl true
@@ -177,11 +181,12 @@ if Code.ensure_loaded?(MyXQL) do
       cte = cte(query, sources)
       {_, name, _} = elem(sources, 0)
 
+      {pre_comments, post_comments} = SQL.comments(query.comments)
       from = from(query, sources)
       join = join(query, sources)
       where = where(query, sources)
 
-      [cte, "DELETE ", name, ".*", from, join | where]
+      [pre_comments, cte, "DELETE ", name, ".*", from, join, where | post_comments]
     end
 
     @impl true
diff --git a/lib/ecto/adapters/postgres/connection.ex b/lib/ecto/adapters/postgres/connection.ex
index 95e893885..6f445fe93 100644
--- a/lib/ecto/adapters/postgres/connection.ex
+++ b/lib/ecto/adapters/postgres/connection.ex
@@ -203,8 +203,10 @@ if Code.ensure_loaded?(Postgrex) do
       limit = limit(query, sources)
       offset = offset(query, sources)
       lock = lock(query, sources)
+      {pre_comments, post_comments} = Ecto.Adapters.SQL.comments(query.comments)
 
       [
+        pre_comments,
         cte,
         select,
         from,
@@ -216,7 +218,8 @@ if Code.ensure_loaded?(Postgrex) do
         combinations,
         order_by,
         limit,
-        offset | lock
+        offset,
+        lock | post_comments
       ]
     end
 
@@ -225,13 +228,13 @@ if Code.ensure_loaded?(Postgrex) do
       sources = create_names(query, [])
       cte = cte(query, sources)
       {from, name} = get_source(query, sources, 0, source)
-
+      {pre_comments, post_comments} = Ecto.Adapters.SQL.comments(query.comments)
       prefix = prefix || ["UPDATE ", from, " AS ", name | " SET "]
       fields = update_fields(query, sources)
       {join, wheres} = using_join(query, :update_all, "FROM", sources)
       where = where(%{query | wheres: wheres ++ query.wheres}, sources)
 
-      [cte, prefix, fields, join, where | returning(query, sources)]
+      [pre_comments, cte, prefix, fields, join, where, returning(query, sources) | post_comments]
     end
 
     @impl true
@@ -239,11 +242,11 @@ if Code.ensure_loaded?(Postgrex) do
       sources = create_names(query, [])
       cte = cte(query, sources)
       {from, name} = get_source(query, sources, 0, from)
-
+      {pre_comments, post_comments} = Ecto.Adapters.SQL.comments(query.comments)
       {join, wheres} = using_join(query, :delete_all, "USING", sources)
       where = where(%{query | wheres: wheres ++ query.wheres}, sources)
 
-      [cte, "DELETE FROM ", from, " AS ", name, join, where | returning(query, sources)]
+      [pre_comments, cte, "DELETE FROM ", from, " AS ", name, join, where, returning(query, sources) | post_comments]
     end
 
     @impl true
diff --git a/lib/ecto/adapters/sql.ex b/lib/ecto/adapters/sql.ex
index 4dac125c8..a80ccc4c9 100644
--- a/lib/ecto/adapters/sql.ex
+++ b/lib/ecto/adapters/sql.ex
@@ -985,12 +985,8 @@ defmodule Ecto.Adapters.SQL do
 
     sql = conn.insert(prefix, source, header, rows, on_conflict, returning, placeholders, opts)
 
-    opts =
-      if is_nil(Keyword.get(opts, :cache_statement)) do
-        [{:cache_statement, "ecto_insert_all_#{source}"} | opts]
-      else
-        opts
-      end
+    opts = put_default_cache_statement(opts, "ecto_insert_all_#{source}")
+    sql = wrap_comments(sql, opts)
 
     all_params = placeholders ++ Enum.reverse(params, conflict_params)
 
@@ -1171,6 +1167,69 @@ defmodule Ecto.Adapters.SQL do
     end
   end
 
+  @doc false
+  def wrap_comments(sql, opts) do
+    {pre, post} = comments(Keyword.get(opts, :comments, []))
+    [pre, sql | post]
+  end
+
+  # Comments become part of the statement text, so a varying comment under a
+  # fixed cache name would make the driver close and re-prepare the statement
+  # on every call (drivers compare the cached text). Skip the default statement
+  # cache whenever comments are given; an explicit :cache_statement still wins,
+  # which keeps caching available for callers with static comments.
+  @doc false
+  def put_default_cache_statement(opts, name) do
+    if is_nil(Keyword.get(opts, :cache_statement)) and Keyword.get(opts, :comments, []) == [] do
+      [{:cache_statement, name} | opts]
+    else
+      opts
+    end
+  end
+
+  @doc false
+  def comments(comments) when is_list(comments) do
+    # The space after `/*` is load-bearing: MySQL executable comments (`/*!`),
+    # MariaDB executable comments (`/*M!`), and optimizer hints (`/*+`) only
+    # take effect when the marker immediately follows `/*`. Keep the space even
+    # though validate_comment!/1 also rejects those prefixes (defense in depth).
+    {pre, post} =
+      Enum.reduce(comments, {[], []}, fn
+        {:pre, c}, {pre, post} -> {[["/* ", validate_comment!(c), " */ "] | pre], post}
+        {:post, c}, {pre, post} -> {pre, [[" /* ", validate_comment!(c), " */"] | post]}
+        other, _ -> raise ArgumentError, "expected {:pre, string} or {:post, string}, got: #{inspect(other)}"
+      end)
+
+    {Enum.reverse(pre), Enum.reverse(post)}
+  end
+
+  def comments(other) do
+    raise ArgumentError,
+          "comments must be a keyword list of [pre: string, post: string], got: #{inspect(other)}"
+  end
+
+  defp validate_comment!(comment) when is_binary(comment) do
+    if String.contains?(comment, ["/*", "*/", <<0>>]) do
+      raise ArgumentError,
+            "a comment cannot contain `/*`, `*/`, or null bytes, got: #{inspect(comment)}"
+    end
+
+    # Placed right after `/*`, these prefixes would form MySQL/MariaDB
+    # executable comments (`/*!...*/`, `/*M!...*/`) or optimizer hints
+    # (`/*+...*/`), turning the comment into SQL that executes.
+    if String.starts_with?(comment, ["!", "+", "M!"]) do
+      raise ArgumentError,
+            "a comment cannot start with `!`, `+`, or `M!`, as MySQL and MariaDB " <>
+              "treat such comments as executable SQL or optimizer hints, got: #{inspect(comment)}"
+    end
+
+    comment
+  end
+
+  defp validate_comment!(other) do
+    raise ArgumentError, "a comment must be a string, got: #{inspect(other)}"
+  end
+
   @doc false
   def struct(
         adapter_meta,
@@ -1184,12 +1243,8 @@ defmodule Ecto.Adapters.SQL do
         returning,
         opts
       ) do
-    opts =
-      if is_nil(Keyword.get(opts, :cache_statement)) do
-        [{:cache_statement, "ecto_#{operation}_#{source}_#{length(params)}"} | opts]
-      else
-        opts
-      end
+    opts = put_default_cache_statement(opts, "ecto_#{operation}_#{source}_#{length(params)}")
+    sql = wrap_comments(sql, opts)
 
     case query(adapter_meta, sql, values, [source: source] ++ opts) do
       {:ok, %{rows: nil, num_rows: 1}} ->
diff --git a/lib/ecto/adapters/tds/connection.ex b/lib/ecto/adapters/tds/connection.ex
index 170b832fa..206f238d5 100644
--- a/lib/ecto/adapters/tds/connection.ex
+++ b/lib/ecto/adapters/tds/connection.ex
@@ -170,11 +170,12 @@ if Code.ensure_loaded?(Tds) do
       # limit = is handled in select (TOP X)
       offset = offset(query, sources)
       lock = lock(query, sources)
+      {pre_comments, post_comments} = SQL.comments(query.comments)
 
       if query.offset != nil and query.order_bys == [],
         do: error!(query, "ORDER BY is mandatory when OFFSET is set")
 
-      [cte, select, from, join, where, group_by, having, combinations, order_by, lock | offset]
+      [pre_comments, cte, select, from, join, where, group_by, having, combinations, order_by, lock, offset | post_comments]
     end
 
     @impl true
@@ -188,8 +189,10 @@ if Code.ensure_loaded?(Tds) do
       join = join(query, sources)
       where = where(query, sources)
       lock = lock(query, sources)
+      {pre_comments, post_comments} = SQL.comments(query.comments)
 
       [
+        pre_comments,
         cte,
         "UPDATE ",
         name,
@@ -198,7 +201,8 @@ if Code.ensure_loaded?(Tds) do
         returning(query, 0, "INSERTED"),
         from,
         join,
-        where | lock
+        where,
+        lock | post_comments
       ]
     end
 
@@ -213,8 +217,9 @@ if Code.ensure_loaded?(Tds) do
       join = join(query, sources)
       where = where(query, sources)
       lock = lock(query, sources)
+      {pre_comments, post_comments} = SQL.comments(query.comments)
 
-      [cte, delete, returning(query, 0, "DELETED"), from, join, where | lock]
+      [pre_comments, cte, delete, returning(query, 0, "DELETED"), from, join, where, lock | post_comments]
     end
 
     @impl true
diff --git a/mix.exs b/mix.exs
index fcc8392fb..0a9ec9515 100644
--- a/mix.exs
+++ b/mix.exs
@@ -84,7 +84,7 @@ defmodule EctoSQL.MixProject do
     if path = System.get_env("ECTO_PATH") do
       {:ecto, path: path}
     else
-      {:ecto, git: "https://github.com/elixir-ecto/ecto.git"}
+      {:ecto, git: "https://github.com/alesasnouski/ecto.git", branch: "master"}
     end
   end
 
diff --git a/test/ecto/adapters/myxql_test.exs b/test/ecto/adapters/myxql_test.exs
index 9170a945c..3912c3976 100644
--- a/test/ecto/adapters/myxql_test.exs
+++ b/test/ecto/adapters/myxql_test.exs
@@ -595,6 +595,21 @@ defmodule Ecto.Adapters.MyXQLTest do
     assert all(query) == ~s{SELECT TRUE FROM `schema` AS s0 UPDATE on s0}
   end
 
+  test "comments" do
+    query = Schema |> select([], true) |> plan()
+    assert all(%{query | comments: [pre: "q"]}) == ~s{/* q */ SELECT TRUE FROM `schema` AS s0}
+    assert all(%{query | comments: [post: "q"]}) == ~s{SELECT TRUE FROM `schema` AS s0 /* q */}
+
+    assert all(%{query | comments: [pre: "a", post: "b"]}) ==
+             ~s{/* a */ SELECT TRUE FROM `schema` AS s0 /* b */}
+
+    query = Schema |> update([], set: [x: 0]) |> plan(:update_all)
+    assert update_all(%{query | comments: [pre: "upd_q"]}) == ~s{/* upd_q */ UPDATE `schema` AS s0 SET s0.`x` = 0}
+
+    query = Schema |> plan(:delete_all)
+    assert delete_all(%{query | comments: [pre: "del_q"]}) == ~s{/* del_q */ DELETE s0.* FROM `schema` AS s0}
+  end
+
   test "string escape" do
     query = "schema" |> where(foo: "'\\  ") |> select([], true) |> plan()
     assert all(query) == ~s{SELECT TRUE FROM `schema` AS s0 WHERE (s0.`foo` = '''\\\\  ')}
diff --git a/test/ecto/adapters/postgres_test.exs b/test/ecto/adapters/postgres_test.exs
index 764c0a4c2..125cf4b4f 100644
--- a/test/ecto/adapters/postgres_test.exs
+++ b/test/ecto/adapters/postgres_test.exs
@@ -788,6 +788,21 @@ defmodule Ecto.Adapters.PostgresTest do
     assert all(query) == ~s{SELECT TRUE FROM "schema" AS s0 UPDATE on s0}
   end
 
+  test "comments" do
+    query = Schema |> select([], true) |> plan()
+    assert all(%{query | comments: [pre: "q"]}) == ~s{/* q */ SELECT TRUE FROM "schema" AS s0}
+    assert all(%{query | comments: [post: "q"]}) == ~s{SELECT TRUE FROM "schema" AS s0 /* q */}
+
+    assert all(%{query | comments: [pre: "a", post: "b"]}) ==
+             ~s{/* a */ SELECT TRUE FROM "schema" AS s0 /* b */}
+
+    query = Schema |> update([], set: [x: 0]) |> plan(:update_all)
+    assert update_all(%{query | comments: [pre: "upd_q"]}) == ~s{/* upd_q */ UPDATE "schema" AS s0 SET "x" = 0}
+
+    query = Schema |> plan(:delete_all)
+    assert delete_all(%{query | comments: [pre: "del_q"]}) == ~s{/* del_q */ DELETE FROM "schema" AS s0}
+  end
+
   test "string escape" do
     query = "schema" |> where(foo: "'\\  ") |> select([], true) |> plan()
     assert all(query) == ~s{SELECT TRUE FROM \"schema\" AS s0 WHERE (s0.\"foo\" = '''\\  ')}
diff --git a/test/ecto/adapters/sql_test.exs b/test/ecto/adapters/sql_test.exs
new file mode 100644
index 000000000..688c7be7f
--- /dev/null
+++ b/test/ecto/adapters/sql_test.exs
@@ -0,0 +1,118 @@
+defmodule Ecto.Adapters.SQLTest do
+  use ExUnit.Case, async: true
+
+  defp comments(list) do
+    {pre, post} = Ecto.Adapters.SQL.comments(list)
+    {IO.iodata_to_binary(pre), IO.iodata_to_binary(post)}
+  end
+
+  defp wrap(sql, opts) do
+    sql |> Ecto.Adapters.SQL.wrap_comments(opts) |> IO.iodata_to_binary()
+  end
+
+  describe "comments/1" do
+    test "empty list renders nothing" do
+      assert comments([]) == {"", ""}
+    end
+
+    test "renders :pre leading and :post trailing" do
+      assert comments(pre: "list_users") == {"/* list_users */ ", ""}
+      assert comments(post: "list_users") == {"", " /* list_users */"}
+      assert comments(pre: "a", post: "b") == {"/* a */ ", " /* b */"}
+    end
+
+    test "preserves order and supports multiples" do
+      assert comments(pre: "a", pre: "b") == {"/* a */ /* b */ ", ""}
+    end
+
+    test "rejects comment-delimiter sequences and null bytes" do
+      for bad <- ["evil */ x", "evil /* x", "x\0y"] do
+        assert_raise ArgumentError, ~r/cannot contain/, fn ->
+          Ecto.Adapters.SQL.comments(pre: bad)
+        end
+      end
+    end
+
+    test "rejects prefixes that MySQL/MariaDB treat as executable comments or hints" do
+      for bad <- ["!40000 DROP TABLE posts", "+MAX_EXECUTION_TIME(1)", "M!100000 DROP"] do
+        assert_raise ArgumentError, ~r/cannot start with/, fn ->
+          Ecto.Adapters.SQL.comments(pre: bad)
+        end
+
+        assert_raise ArgumentError, ~r/cannot start with/, fn ->
+          Ecto.Adapters.SQL.comments(post: bad)
+        end
+      end
+    end
+
+    # Regression: the space after `/*` is load-bearing. MySQL/MariaDB executable
+    # comments (`/*!`, `/*M!`) and optimizer hints (`/*+`) only take effect when
+    # the marker immediately follows `/*`, so the rendered form must always keep
+    # a space between the delimiter and the comment text.
+    test "always renders a space between /* and the comment text" do
+      {pre, post} = comments(pre: "tag", post: "tag")
+      assert pre == "/* tag */ "
+      assert post == " /* tag */"
+      refute pre =~ "/*t"
+      refute post =~ "/*t"
+    end
+
+    test "rejects bad shapes" do
+      assert_raise ArgumentError, ~r/expected \{:pre/, fn ->
+        Ecto.Adapters.SQL.comments(foo: "bar")
+      end
+
+      assert_raise ArgumentError, ~r/keyword list/, fn ->
+        Ecto.Adapters.SQL.comments("nope")
+      end
+    end
+  end
+
+  describe "wrap_comments/2" do
+    test "wraps the sql with pre/post from the :comments option" do
+      assert wrap("INSERT INTO posts ...", comments: [pre: "create_post", post: "v2"]) ==
+               "/* create_post */ INSERT INTO posts ... /* v2 */"
+    end
+
+    test "is a no-op without the :comments option" do
+      assert wrap("INSERT INTO posts ...", timeout: 5000) == "INSERT INTO posts ..."
+    end
+  end
+
+  describe "put_default_cache_statement/2" do
+    test "sets the default name" do
+      opts = Ecto.Adapters.SQL.put_default_cache_statement([timeout: 5000], "ecto_insert_posts")
+      assert Keyword.get(opts, :cache_statement) == "ecto_insert_posts"
+    end
+
+    test "honors an explicit :cache_statement" do
+      opts = Ecto.Adapters.SQL.put_default_cache_statement([cache_statement: "mine"], "default")
+      assert Keyword.get(opts, :cache_statement) == "mine"
+    end
+
+    test "skips the default when comments are given" do
+      opts =
+        Ecto.Adapters.SQL.put_default_cache_statement(
+          [comments: [pre: "dyn_123"]],
+          "ecto_insert_posts"
+        )
+
+      assert Keyword.get(opts, :cache_statement) == nil
+    end
+
+    test "an explicit :cache_statement wins even with comments" do
+      opts =
+        Ecto.Adapters.SQL.put_default_cache_statement(
+          [comments: [pre: "static_tag"], cache_statement: "mine"],
+          "default"
+        )
+
+      assert Keyword.get(opts, :cache_statement) == "mine"
+    end
+
+    test "an empty :comments list still gets the default" do
+      opts = Ecto.Adapters.SQL.put_default_cache_statement([comments: []], "ecto_insert_posts")
+      assert Keyword.get(opts, :cache_statement) == "ecto_insert_posts"
+    end
+  end
+end
diff --git a/test/ecto/adapters/tds_test.exs b/test/ecto/adapters/tds_test.exs
index 2e94de197..c006a9e60 100644
--- a/test/ecto/adapters/tds_test.exs
+++ b/test/ecto/adapters/tds_test.exs
@@ -646,6 +646,21 @@ defmodule Ecto.Adapters.TdsTest do
     assert all(query) == ~s{SELECT CAST(1 as bit) FROM [schema] AS s0 OPTION (UPDATE on s0)}
   end
 
+  test "comments" do
+    query = Schema |> select([], true) |> plan()
+    assert all(%{query | comments: [pre: "q"]}) == ~s{/* q */ SELECT CAST(1 as bit) FROM [schema] AS s0}
+    assert all(%{query | comments: [post: "q"]}) == ~s{SELECT CAST(1 as bit) FROM [schema] AS s0 /* q */}
+
+    assert all(%{query | comments: [pre: "a", post: "b"]}) ==
+             ~s{/* a */ SELECT CAST(1 as bit) FROM [schema] AS s0 /* b */}
+
+    query = Schema |> update([], set: [x: 0]) |> plan(:update_all)
+    assert update_all(%{query | comments: [pre: "upd_q"]}) == ~s{/* upd_q */ UPDATE s0 SET s0.[x] = 0 FROM [schema] AS s0}
+
+    query = Schema |> plan(:delete_all)
+    assert delete_all(%{query | comments: [pre: "del_q"]}) == ~s{/* del_q */ DELETE s0 FROM [schema] AS s0}
+  end
+
   test "string escape" do
     query = "schema" |> where(foo: "\'--  ") |> select([], true) |> plan()