Merge

mysql-test/r/select.result:
  Auto merged
mysql-test/t/select.test:
  Auto merged
sql/filesort.cc:
  Auto merged
sql/item.cc:
  SCCS merged

mysql-test/r/select.result

@@ -2423,3 +2423,26 @@ SELECT * FROM t1 WHERE city LIKE '%london%' AND city='London';
 city
 London
 DROP TABLE t1;
+create table t1 (a int(11) unsigned, b int(11) unsigned);
+insert into t1 values (1,0), (1,1), (1,2);
+select a-b  from t1 order by 1;
+a-b
+0
+1
+18446744073709551615
+select a-b , (a-b < 0)  from t1 order by 1;
+a-b	(a-b < 0)
+0	0
+1	0
+18446744073709551615	0
+select a-b as d, (a-b >= 0), b from t1 group by b having d >= 0;
+d	(a-b >= 0)	b
+1	1	0
+0	1	1
+18446744073709551615	1	2
+select cast((a - b) as unsigned) from t1 order by 1;
+cast((a - b) as unsigned)
+0
+1
+18446744073709551615
+drop table t1;

mysql-test/t/select.test

@@ -2004,3 +2004,14 @@ SELECT * FROM t1 WHERE city LIKE '%london%' AND city='London';
 
 DROP TABLE t1;
 
+#
+# Bug#7425 inconsistent sort order on unsigned columns result of substraction
+#
+
+create table t1 (a int(11) unsigned, b int(11) unsigned);
+insert into t1 values (1,0), (1,1), (1,2);
+select a-b  from t1 order by 1;
+select a-b , (a-b < 0)  from t1 order by 1;
+select a-b as d, (a-b >= 0), b from t1 group by b having d >= 0;
+select cast((a - b) as unsigned) from t1 order by 1;
+drop table t1;

sql/filesort.cc

@@ -694,12 +694,18 @@ static void make_sortkey(register SORTPARAM *param,
 	  to[3]= (uchar) (value >> 32);
 	  to[2]= (uchar) (value >> 40);
 	  to[1]= (uchar) (value >> 48);
-	  to[0]= (uchar) (value >> 56) ^ 128;	// Fix sign
+          if (item->unsigned_flag)                    /* Fix sign */
+            to[0]= (uchar) (value >> 56);
+          else
+            to[0]= (uchar) (value >> 56) ^ 128;	/* Reverse signbit */
 #else
 	  to[3]= (uchar) value;
 	  to[2]= (uchar) (value >> 8);
 	  to[1]= (uchar) (value >> 16);
-	  to[0]= (uchar) (value >> 24) ^ 128;	// Fix sign
+          if (item->unsigned_flag)                    /* Fix sign */
+            to[0]= (uchar) (value >> 24);
+          else
+            to[0]= (uchar) (value >> 24) ^ 128;	/* Reverse signbit */
 #endif
 	  break;
 	}

sql/item.cc

@@ -3717,6 +3717,7 @@ void Item_ref::set_properties()
     split_sum_func() doesn't try to change the reference.
   */
   with_sum_func= (*ref)->with_sum_func;
+  unsigned_flag= (*ref)->unsigned_flag;
   if ((*ref)->type() == FIELD_ITEM)
     alias_name_used= ((Item_ident *) (*ref))->alias_name_used;
   else