Fixed bug #27348.

If a set function with a outer reference s(outer_ref) cannot be aggregated 
the outer query against which the reference has been resolved then MySQL
interpretes s(outer_ref) in the same way as it would interpret s(const).
Hovever the standard requires throwing an error in this situation.
Added some code to support this requirement in ansi mode.
Corrected another minor bug in Item_sum::check_sum_func.
 

mysql-test/r/subselect.result

@@ -3924,3 +3924,26 @@ c	a	(SELECT GROUP_CONCAT(COUNT(a)+1) FROM t2 WHERE m = a)
 3	3	4
 1	4	2,2
 DROP table t1,t2;
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 VALUES (2,22),(1,11),(2,22);
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 0 GROUP BY a;
+a
+1
+2
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 1 GROUP BY a;
+a
+SELECT a FROM t1 t0
+WHERE (SELECT COUNT(t0.b) FROM t1 t WHERE t.b>20) GROUP BY a;
+a
+1
+2
+SET @@sql_mode='ansi';
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 0 GROUP BY a;
+ERROR HY000: Invalid use of group function
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 1 GROUP BY a;
+ERROR HY000: Invalid use of group function
+SELECT a FROM t1 t0
+WHERE (SELECT COUNT(t0.b) FROM t1 t WHERE t.b>20) GROUP BY a;
+ERROR HY000: Invalid use of group function
+SET @@sql_mode=default;
+DROP TABLE t1;

mysql-test/t/subselect.test

@@ -2782,3 +2782,30 @@ SELECT COUNT(*) c, a,
   FROM t1 GROUP BY a;
 
 DROP table t1,t2;
+
+#
+# Bug #27348: SET FUNCTION used in  a subquery from WHERE condition 
+#  
+
+CREATE TABLE t1 (a int, b int);
+INSERT INTO t1 VALUES (2,22),(1,11),(2,22);
+
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 0 GROUP BY a;
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 1 GROUP BY a;
+
+SELECT a FROM t1 t0
+  WHERE (SELECT COUNT(t0.b) FROM t1 t WHERE t.b>20) GROUP BY a;
+
+SET @@sql_mode='ansi';
+--error 1111
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 0 GROUP BY a;
+--error 1111
+SELECT a FROM t1 WHERE (SELECT COUNT(b) FROM DUAL) > 1 GROUP BY a;
+
+--error 1111
+SELECT a FROM t1 t0
+  WHERE (SELECT COUNT(t0.b) FROM t1 t WHERE t.b>20) GROUP BY a;
+
+SET @@sql_mode=default;
+
+DROP TABLE t1;

sql/item_sum.cc

@@ -149,6 +149,8 @@ bool Item_sum::check_sum_func(THD *thd, Item **ref)
     if (register_sum_func(thd, ref))
       return TRUE;
     invalid= aggr_level < 0 && !(allow_sum_func & (1 << nest_level));
+    if (!invalid && thd->variables.sql_mode & MODE_ANSI)
+      invalid= aggr_level < 0 && max_arg_level < nest_level;
   }
   if (!invalid && aggr_level < 0)
   {
@@ -164,8 +166,9 @@ bool Item_sum::check_sum_func(THD *thd, Item **ref)
     Additionally we have to check whether possible nested set functions
     are acceptable here: they are not, if the level of aggregation of
     some of them is less than aggr_level.
-  */ 
-  invalid= aggr_level <= max_sum_func_level;
+  */
+  if (!invalid) 
+    invalid= aggr_level <= max_sum_func_level;
   if (invalid)  
   {
     my_message(ER_INVALID_GROUP_FUNC_USE, ER(ER_INVALID_GROUP_FUNC_USE),