1 files changed, 20 insertions, 16 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 14136435a50..4226f58e9a6 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -2486,6 +2486,7 @@ Item_type_holder::Item_type_holder(THD *thd, Item *item)
   else
     field_example= 0;
   max_length= real_length(item);
+  maybe_null= item->maybe_null;
   collation.set(item->collation);
 }
 
@@ -2509,31 +2510,36 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
   bool change_field= 0, skip_store_field= 0;
   Item_result new_type= type_convertor[item_type][item->result_type()];
 
-  // we have both fields
+  /*
+    we have both fields and field is not enum or set(different enums(sets)
+    can't be joinned in one enum(set) field)
+  */
   if (field_example && item->type() == Item::FIELD_ITEM)
   {
     Field *field= ((Item_field *)item)->field;
-    if (field_example->field_cast_type() != field->field_cast_type())
+    /* Can old example field store new data? */
+    if ((change_field=
+          !field->field_cast_compatible(field_example->field_cast_type())))
     {
-      if (!(change_field=
-	    field_example->field_cast_compatible(field->field_cast_type())))
-      {
-	/*
-	  if old field can't store value of 'worse' new field we will make
-	  decision about result field type based only on Item result type
-	*/
-	if (!field->field_cast_compatible(field_example->field_cast_type()))
-	  skip_store_field= 1;
-      }
+      /*
+        if old field can't store value of 'worse' new field we will make
+        decision about result field type based only on Item result type
+      */
+      if (!field_example->field_cast_compatible(field->field_cast_type()))
+        skip_store_field= 1;
     }
   }
+  else if (field_example || item->type() == Item::FIELD_ITEM)
+  {
+    /* expression can't be mixed with field */
+    skip_store_field= 1;
+  }
 
   // size/type should be changed
   if (change_field ||
+      skip_store_field ||
       (new_type != item_type) ||
       (max_length < new_length) ||
-      ((new_type == INT_RESULT) &&
-       (decimals < item->decimals)) ||
       (!maybe_null && item->maybe_null) ||
       (item_type == STRING_RESULT && new_type == STRING_RESULT &&
        !my_charset_same(collation.collation, item->collation.collation)))
@@ -2541,8 +2547,6 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
     // new field has some parameters worse then current
     skip_store_field|= (change_field &&
 			(max_length > new_length) ||
-			((new_type == INT_RESULT) &&
-			 (decimals > item->decimals)) ||
 			(maybe_null && !item->maybe_null) ||
 			(item_type == STRING_RESULT &&
 			 new_type == STRING_RESULT &&