fixed bug of subselect in derived tables

mysql-test/r/subselect.result:
  test of subselect in derived table
mysql-test/t/subselect.test:
  test of subselect in derived table

mysql-test/r/subselect.result

@@ -30,6 +30,8 @@ Unknown column 'a' in 'field list'
 SELECT 1 as a FROM (SELECT 1) HAVING (SELECT a)=1;
 a
 1
+SELECT 1 FROM (SELECT (SELECT a));
+Unknown column 'a' in 'field list'
 drop table if exists t1,t2,t3,t4,t5,t6,t7,t8;
 create table t1 (a int);
 create table t2 (a int, b int);

mysql-test/t/subselect.test

@@ -13,6 +13,8 @@ SELECT 1 FROM (SELECT 1 as a) HAVING (SELECT a)=1;
 -- error 1054
 SELECT (SELECT 1), a;
 SELECT 1 as a FROM (SELECT 1) HAVING (SELECT a)=1;
+-- error 1054
+SELECT 1 FROM (SELECT (SELECT a));
 drop table if exists t1,t2,t3,t4,t5,t6,t7,t8;
 create table t1 (a int);
 create table t2 (a int, b int);

sql/item.cc

@@ -472,7 +472,8 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 				       REPORT_EXCEPT_NOT_FOUND)) !=
 	     (Item **)not_found_item)
 	    break;
-	  
+	  if (sl->linkage == DERIVED_TABLE_TYPE)
+	    break; // do not look over derived table
 	}
       if (!tmp)
 	return -1;
@@ -887,6 +888,8 @@ bool Item_ref::fix_fields(THD *thd,TABLE_LIST *tables, Item **reference)
 	if ((tmp= find_field_in_tables(thd, this,
 				       sl->get_table_list(),
 				       0)) != not_found_field);
+	if (sl->linkage == DERIVED_TABLE_TYPE)
+	  break; // do not look over derived table
       }
 
       if (!ref)