diff --git a/swad_chat_database.c b/swad_chat_database.c
new file mode 100644
index 000000000..cde6c6f1e
--- /dev/null
+++ b/swad_chat_database.c
@@ -0,0 +1,77 @@
+// swad_chat_database.c: chat operations with database
+
+/*
+    SWAD (Shared Workspace At a Distance),
+    is a web platform developed at the University of Granada (Spain),
+    and used to support university teaching.
+
+    This file is part of SWAD core.
+    Copyright (C) 1999-2021 Antonio Caņas Vargas
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as
+    published by the Free Software Foundation, either version 3 of the
+    License, or (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/*****************************************************************************/
+/********************************* Headers ***********************************/
+/*****************************************************************************/
+
+#include <mysql/mysql.h>	// To access MySQL databases
+
+#include "swad_chat.h"
+#include "swad_chat_database.h"
+#include "swad_database.h"
+#include "swad_global.h"
+
+/*****************************************************************************/
+/************** External global variables from others modules ****************/
+/*****************************************************************************/
+
+extern struct Globals Gbl;
+
+/*****************************************************************************/
+/***************************** Private constants *****************************/
+/*****************************************************************************/
+
+/*****************************************************************************/
+/***************************** Private prototypes ****************************/
+/*****************************************************************************/
+
+/*****************************************************************************/
+/********************** Get list of chat rooms with users ********************/
+/*****************************************************************************/
+
+unsigned Cht_DB_GetListOfChatRoomsWithUsrs (MYSQL_RES **mysql_res)
+  {
+   return (unsigned)
+   DB_QuerySELECT (mysql_res,"can not get chat rooms with connected users",
+		   "SELECT RoomCode,"		// row[0]
+			  "NumUsrs"		// row[1]
+		    " FROM cht_rooms"
+		   " WHERE NumUsrs>0"
+		   " ORDER BY NumUsrs DESC,"
+			     "RoomCode");
+  }
+
+/*****************************************************************************/
+/*************** Get number of users connected to a chat room ****************/
+/*****************************************************************************/
+
+unsigned Cht_DB_GetNumUsrsInChatRoom (const char *RoomCode)
+  {
+   return DB_QuerySELECTUnsigned ("can not get number of users"
+				  " connected to a chat room",
+				  "SELECT NumUsrs"
+				   " FROM cht_rooms"
+				  " WHERE RoomCode='%s'",
+				  RoomCode);
+  }
diff --git a/swad_chat_database.h b/swad_chat_database.h
new file mode 100644
index 000000000..a7d9ee48c
--- /dev/null
+++ b/swad_chat_database.h
@@ -0,0 +1,47 @@
+// swad_chat_database.h: chat operations with database
+
+#ifndef _SWAD_CHT_DB
+#define _SWAD_CHT_DB
+/*
+    SWAD (Shared Workspace At a Distance),
+    is a web platform developed at the University of Granada (Spain),
+    and used to support university teaching.
+
+    This file is part of SWAD core.
+    Copyright (C) 1999-2021 Antonio Caņas Vargas
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as
+    published by the Free Software Foundation, either version 3 of the
+    License, or (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/*****************************************************************************/
+/********************************* Headers ***********************************/
+/*****************************************************************************/
+
+#include <mysql/mysql.h>	// To access MySQL databases
+
+/*****************************************************************************/
+/***************************** Public constants ******************************/
+/*****************************************************************************/
+
+/*****************************************************************************/
+/******************************* Public types ********************************/
+/*****************************************************************************/
+
+/*****************************************************************************/
+/***************************** Public prototypes *****************************/
+/*****************************************************************************/
+
+unsigned Cht_DB_GetListOfChatRoomsWithUsrs (MYSQL_RES **mysql_res);
+unsigned Cht_DB_GetNumUsrsInChatRoom (const char *RoomCode);
+
+#endif