sql_select.cc, item_cmpfunc.h:

  After merge fix for collation.

sql/item_cmpfunc.h

@@ -1020,6 +1020,8 @@ class Item_equal: public Item_bool_func
   bool walk(Item_processor processor, byte *arg);
   Item *transform(Item_transformer transformer, byte *arg);
   void print(String *str);
+  CHARSET_INFO *compare_collation() 
+  { return fields.head()->collation.collation; }
 }; 
 
 class COND_EQUAL

sql/sql_select.cc

@@ -4539,6 +4539,12 @@ static bool check_equality(Item *item, COND_EQUAL *cond_equal)
           field_item->result_type() == const_item->result_type())
       {
         bool copyfl;
+
+        if (field_item->result_type() == STRING_RESULT &&
+              ((Field_str *) field_item)->charset() !=
+               ((Item_cond *) item)->compare_collation())
+          return FALSE;
+
         Item_equal *item_equal = find_item_equal(cond_equal,
                                                  field_item->field, &copyfl);
         if (copyfl)