Fix bug #11399 Column alias was lost during view preraration.

New item created in find_field_in_table() to fix view's item, was created 
without taking into account original item's alias. This patch checks if alias 
is set to the original item and if so sets it to newly created item.

mysql-test/r/view.result

@@ -1863,3 +1863,11 @@ ERROR HY000: Field of view 'test.v2' underlying table doesn't have a default val
 set sql_mode=default;
 drop view v2,v1;
 drop table t1;
+create table t1 (f1 int);
+insert into t1 values (1);
+create view v1 as select f1 from t1;
+select f1 as alias from v1;
+alias
+1
+drop view v1;
+drop table t1;

mysql-test/t/view.test

@@ -1714,3 +1714,13 @@ INSERT INTO v2 (vcol1) VALUES(12);
 set sql_mode=default;
 drop view v2,v1;
 drop table t1;
+
+#
+# Bug#11399 Use an alias in a select statement on a view
+#
+create table t1 (f1 int);
+insert into t1 values (1);
+create view v1 as select f1 from t1;
+select f1 as alias from v1;
+drop view v1;
+drop table t1;

sql/sql_base.cc

@@ -2407,9 +2407,11 @@ Field *view_ref_found= (Field*) 0x2;
     name			name of field
     item_name                   name of item if it will be created (VIEW)
     length			length of name
-    ref				expression substituted in VIEW should be
+    ref	[in/out]		expression substituted in VIEW should be
 				  passed using this reference (return
 				  view_ref_found)
+                                  (*ref != NULL) only if *ref contains
+                                  the item that we need to replace.
     check_grants_table		do check columns grants for table?
     check_grants_view		do check columns grants for view?
     allow_rowid			do allow finding of "_rowid" field?
@@ -2447,11 +2449,6 @@ find_field_in_table(THD *thd, TABLE_LIST *table_list,
     {
       if (!my_strcasecmp(system_charset_info, field_it.name(), name))
       {
-        Item *item= field_it.create_item(thd);
-        if (!item)
-        {
-          DBUG_RETURN(0);
-        }
         if (table_list->schema_table_reformed)
         {
           /*
@@ -2470,6 +2467,19 @@ find_field_in_table(THD *thd, TABLE_LIST *table_list,
 			       name, length))
 	  DBUG_RETURN(WRONG_GRANT);
 #endif
+        Item *item= field_it.create_item(thd);
+        if (!item)
+        {
+          DBUG_RETURN(0);
+        }
+        /*
+          *ref != NULL means that *ref contains the item that we need to
+          replace. If the item was aliased by the user, set the alias to
+          the replacing item.
+         */
+        if (*ref && !(*ref)->is_autogenerated_name)
+          item->set_name((*ref)->name, (*ref)->name_length,
+                         system_charset_info);
         if (register_tree_change)
           thd->change_item_tree(ref, item);
         else