diff --git a/src/mod_admin_update_sql.erl b/src/mod_admin_update_sql.erl
index ec86cece7..f3a458a96 100644
--- a/src/mod_admin_update_sql.erl
+++ b/src/mod_admin_update_sql.erl
@@ -63,7 +63,7 @@ depends(_Host, _Opts) ->
 
 get_commands_spec() ->
     [#ejabberd_commands{name = update_sql, tags = [sql],
-                        desc = "Convert MySQL or PostgreSQL DB to the new format",
+                        desc = "Convert MS SQL, MySQL or PostgreSQL DB to the new format",
                         module = ?MODULE, function = update_sql,
                         args = [],
                         args_example = [],
@@ -93,6 +93,7 @@ update_sql(Host) ->
     DBType = ejabberd_option:sql_type(LHost),
     IsSupported =
         case DBType of
+            mssql -> true;
             mysql -> true;
             pgsql -> true;
             _ -> false
@@ -139,7 +140,7 @@ update_tables(State) ->
     drop_sh_default(State, "rostergroups"),
 
     add_sh_column(State, "sr_group"),
-    add_pkey(State, "sr_group", ["server_host", "name"]),
+    drop_index(State, "sr_group", "i_sr_group_name"),
     create_unique_index(State, "sr_group", "i_sr_group_sh_name", ["server_host", "name"]),
     drop_sh_default(State, "sr_group"),
 
@@ -147,7 +148,6 @@ update_tables(State) ->
     drop_index(State, "sr_user", "i_sr_user_jid_grp"),
     drop_index(State, "sr_user", "i_sr_user_jid"),
     drop_index(State, "sr_user", "i_sr_user_grp"),
-    add_pkey(State, "sr_user", ["server_host", "jid", "grp"]),
     create_unique_index(State, "sr_user", "i_sr_user_sh_jid_grp", ["server_host", "jid", "grp"]),
     create_index(State, "sr_user", "i_sr_user_sh_grp", ["server_host", "grp"]),
     drop_sh_default(State, "sr_user"),
@@ -257,8 +257,8 @@ update_tables(State) ->
     add_sh_column(State, "push_session"),
     drop_index(State, "push_session", "i_push_usn"),
     drop_index(State, "push_session", "i_push_ut"),
-    add_pkey(State, "push_session", ["server_host", "username", "timestamp"]),
     create_unique_index(State, "push_session", "i_push_session_susn", ["server_host", "username", "service", "node"]),
+    create_index(State, "push_session", "i_push_session_sh_username_timestamp", ["server_host", "username", "timestamp"]),
     drop_sh_default(State, "push_session"),
 
     add_sh_column(State, "mix_pam"),
@@ -281,6 +281,12 @@ add_sh_column(#state{dbtype = pgsql} = State, Table) ->
       ["ALTER TABLE ", Table, " ADD COLUMN server_host text NOT NULL DEFAULT '",
        (State#state.escape)(State#state.host),
        "';"]);
+add_sh_column(#state{dbtype = mssql} = State, Table) ->
+    sql_query(
+      State#state.host,
+      ["ALTER TABLE [", Table, "] ADD [server_host] varchar (250) NOT NULL CONSTRAINT [server_host_default] DEFAULT '",
+       (State#state.escape)(State#state.host),
+       "';"]);
 add_sh_column(#state{dbtype = mysql} = State, Table) ->
     sql_query(
       State#state.host,
@@ -292,6 +298,10 @@ drop_pkey(#state{dbtype = pgsql} = State, Table) ->
     sql_query(
       State#state.host,
       ["ALTER TABLE ", Table, " DROP CONSTRAINT ", Table, "_pkey;"]);
+drop_pkey(#state{dbtype = mssql} = State, Table) ->
+    sql_query(
+      State#state.host,
+      ["ALTER TABLE [", Table, "] DROP CONSTRAINT [", Table, "_PRIMARY];"]);
 drop_pkey(#state{dbtype = mysql} = State, Table) ->
     sql_query(
       State#state.host,
@@ -302,6 +312,13 @@ add_pkey(#state{dbtype = pgsql} = State, Table, Cols) ->
     sql_query(
       State#state.host,
       ["ALTER TABLE ", Table, " ADD PRIMARY KEY (", SCols, ");"]);
+add_pkey(#state{dbtype = mssql} = State, Table, Cols) ->
+    SCols = string:join(Cols, "], ["),
+    sql_query(
+      State#state.host,
+      ["ALTER TABLE [", Table, "] ADD CONSTRAINT [", Table, "_PRIMARY] PRIMARY KEY CLUSTERED ([", SCols, "]) ",
+       "WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ",
+       "ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY];"]);
 add_pkey(#state{dbtype = mysql} = State, Table, Cols) ->
     Cols2 = [C ++ mysql_keylen(Table, C) || C <- Cols],
     SCols = string:join(Cols2, ", "),
@@ -313,6 +330,10 @@ drop_sh_default(#state{dbtype = pgsql} = State, Table) ->
     sql_query(
       State#state.host,
       ["ALTER TABLE ", Table, " ALTER COLUMN server_host DROP DEFAULT;"]);
+drop_sh_default(#state{dbtype = mssql} = State, Table) ->
+    sql_query(
+      State#state.host,
+      ["ALTER TABLE [", Table, "] DROP CONSTRAINT [server_host_default];"]);
 drop_sh_default(#state{dbtype = mysql} = State, Table) ->
     sql_query(
       State#state.host,
@@ -322,6 +343,10 @@ drop_index(#state{dbtype = pgsql} = State, _Table, Index) ->
     sql_query(
       State#state.host,
       ["DROP INDEX ", Index, ";"]);
+drop_index(#state{dbtype = mssql} = State, Table, Index) ->
+    sql_query(
+      State#state.host,
+      ["DROP INDEX [", mssql_old_index_name(Index), "] ON [", Table, "];"]);
 drop_index(#state{dbtype = mysql} = State, Table, Index) ->
     sql_query(
       State#state.host,
@@ -333,6 +358,15 @@ create_unique_index(#state{dbtype = pgsql} = State, Table, Index, Cols) ->
       State#state.host,
       ["CREATE UNIQUE INDEX ", Index, " ON ", Table, " USING btree (",
        SCols, ");"]);
+create_unique_index(#state{dbtype = mssql} = State, Table, "i_privacy_list_sh_username_name" = Index, Cols) ->
+    create_index(State, Table, Index, Cols);
+create_unique_index(#state{dbtype = mssql} = State, Table, Index, Cols) ->
+    SCols = string:join(Cols, ", "),
+    sql_query(
+      State#state.host,
+      ["CREATE UNIQUE ", mssql_clustered(Index), "INDEX [", mssql_new_index_name(Index), "] ",
+       "ON [", Table, "] (", SCols, ") ",
+       "WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON);"]);
 create_unique_index(#state{dbtype = mysql} = State, Table, Index, Cols) ->
     Cols2 = [C ++ mysql_keylen(Index, C) || C <- Cols],
     SCols = string:join(Cols2, ", "),
@@ -347,6 +381,12 @@ create_index(#state{dbtype = pgsql} = State, Table, Index, Cols) ->
       State#state.host,
       ["CREATE INDEX ", Index, " ON ", Table, " USING btree (",
        SCols, ");"]);
+create_index(#state{dbtype = mssql} = State, Table, Index, Cols) ->
+    SCols = string:join(Cols, ", "),
+    sql_query(
+      State#state.host,
+      ["CREATE INDEX [", mssql_new_index_name(Index), "] ON [", Table, "] (", SCols, ") ",
+       "WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON);"]);
 create_index(#state{dbtype = mysql} = State, Table, Index, Cols) ->
     Cols2 = [C ++ mysql_keylen(Index, C) || C <- Cols],
     SCols = string:join(Cols2, ", "),
@@ -355,6 +395,33 @@ create_index(#state{dbtype = mysql} = State, Table, Index, Cols) ->
       ["CREATE INDEX ", Index, " ON ", Table, "(",
        SCols, ");"]).
 
+mssql_old_index_name("i_bare_peer") -> "archive_bare_peer";
+mssql_old_index_name("i_peer") -> "archive_peer";
+mssql_old_index_name("i_timestamp") -> "archive_timestamp";
+mssql_old_index_name("i_username") -> "archive_username";
+mssql_old_index_name("i_username_bare_peer") -> "archive_username_bare_peer";
+mssql_old_index_name("i_username_peer") -> "archive_username_peer";
+mssql_old_index_name("i_username_timestamp") -> "archive_username_timestamp";
+mssql_old_index_name("i_push_usn") -> "i_push_usn";
+mssql_old_index_name("i_push_ut") -> "i_push_ut";
+mssql_old_index_name("pk_rosterg_user_jid") -> "rostergroups_username_jid";
+mssql_old_index_name("i_rosteru_jid") -> "rosterusers_jid";
+mssql_old_index_name("i_rosteru_username") -> "rosterusers_username";
+mssql_old_index_name("i_rosteru_user_jid") -> "rosterusers_username_jid";
+mssql_old_index_name("i_despool") -> "spool_username";
+mssql_old_index_name("i_sr_user_jid_grp") -> "sr_user_jid_group";
+mssql_old_index_name(Index) -> string:substr(Index, 3).
+
+mssql_new_index_name("i_rosterg_sh_user_jid") -> "rostergroups_sh_username_jid";
+mssql_new_index_name("i_rosteru_sh_jid") -> "rosterusers_sh_jid";
+mssql_new_index_name("i_rosteru_sh_user_jid") -> "rosterusers_sh_username_jid";
+mssql_new_index_name("i_sr_user_sh_jid_grp") -> "sr_user_sh_jid_group";
+mssql_new_index_name(Index) -> string:substr(Index, 3).
+
+mssql_clustered("i_mix_pam") -> "";
+mssql_clustered("i_push_session_susn") -> "";
+mssql_clustered(_) -> "CLUSTERED ".
+
 mysql_keylen(_, "bare_peer") -> "(191)";
 mysql_keylen(_, "channel") -> "(191)";
 mysql_keylen(_, "domain") -> "(75)";
@@ -389,5 +456,5 @@ mod_doc() ->
           ?T("This module can be used to update existing SQL database "
              "from the default to the new schema. Check the section "
              "http://../database/#default-and-new-schemas[Default and New Schemas] for details. "
-             "Please note that only MySQL and PostgreSQL are supported. "
+             "Please note that only MS SQL, MySQL, and PostgreSQL are supported. "
              "When the module is loaded use _`update_sql`_ API.")}.