Fix for the bug #1209: SELECT DATABASE().

mysql-test/r/create.result

@@ -361,3 +361,16 @@ a	b	c	d	e	f	g	h	dd
 1	-7	7	2000-01-01	b	2000-01-01 00:00:00	05:04:03	yet another binary data	02:00:00
 2	-2	2	1825-12-14	a	2003-01-01 03:02:01	04:03:02	binary data	02:00:00
 drop table t1, t2;
+drop database if exists test_$1;
+create database test_$1;
+use test_$1;
+select database();
+database()
+test_$1
+drop database test_$1;
+select database();
+database()
+NULL
+select database();
+database()
+NULL

mysql-test/t/create.test

@@ -260,3 +260,19 @@ select * from t2;
 
 drop table t1, t2;
 
+#
+# Bug #1209
+#
+
+--disable_warnings
+drop database if exists test_$1;
+--enable_warnings
+create database test_$1;
+use test_$1;
+select database();
+drop database test_$1;
+select database();
+
+# Connect without a database
+connect (user4,localhost,mysqltest_1,,*NO-ONE*);
+select database();

sql/item_strfunc.cc

@@ -1454,8 +1454,8 @@ String *Item_func_database::val_str(String *str)
   THD *thd= current_thd;
   if (!thd->db)
   {
-    str->length(0);
-    str->set_charset(system_charset_info);
+    null_value= 1;
+    return 0;
   }
   else
     str->copy((const char*) thd->db,(uint) strlen(thd->db),system_charset_info);

sql/sql_db.cc

@@ -391,6 +391,8 @@ int mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
 
 exit:
   start_waiting_global_read_lock(thd);
+  if (thd->db && !strcmp(thd->db, db))
+    thd->db= 0;
 exit2:
   VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));