Bug #26186:

When handling DELETE ... FROM if there is no
condition it is internally transformed to 
TRUNCATE for more efficient execution by the
storage handler.
The check for validity of the optional ORDER BY 
clause is done after the check for the above 
optimization and will not be performed if the
optimization can be applied.
Moved the validity check for ORDER BY before 
the optimization so it performed regardless of
the optimization.

mysql-test/r/delete.result

@@ -214,3 +214,12 @@ select count(*) from t1;
 count(*)
 0
 drop table t1;
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1);
+DELETE FROM t1 ORDER BY x;
+ERROR 42S22: Unknown column 'x' in 'order clause'
+DELETE FROM t1 ORDER BY t2.x;
+ERROR 42S22: Unknown column 't2.x' in 'order clause'
+DELETE FROM t1 ORDER BY (SELECT x);
+ERROR 42S22: Unknown column 'x' in 'field list'
+DROP TABLE t1;

mysql-test/t/delete.test

@@ -203,3 +203,21 @@ select * from t1 where a is null;
 delete from t1 where a is null;
 select count(*) from t1;
 drop table t1;
+
+#
+# Bug #26186: delete order by, sometimes accept unknown column
+#
+CREATE TABLE t1 (a INT); INSERT INTO t1 VALUES (1);
+
+--error ER_BAD_FIELD_ERROR
+DELETE FROM t1 ORDER BY x;
+
+# even columns from a table not used in query (and not even existing)
+--error ER_BAD_FIELD_ERROR
+DELETE FROM t1 ORDER BY t2.x;
+
+# subquery (as long as the subquery from is valid or DUAL)
+--error ER_BAD_FIELD_ERROR
+DELETE FROM t1 ORDER BY (SELECT x);
+
+DROP TABLE t1;

sql/sql_delete.cc

@@ -60,6 +60,27 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   if (mysql_prepare_delete(thd, table_list, &conds))
     DBUG_RETURN(TRUE);
 
+  /* check ORDER BY even if it can be ignored */
+  if (order && order->elements)
+  {
+    TABLE_LIST   tables;
+    List<Item>   fields;
+    List<Item>   all_fields;
+
+    bzero((char*) &tables,sizeof(tables));
+    tables.table = table;
+    tables.alias = table_list->alias;
+
+      if (select_lex->setup_ref_array(thd, order->elements) ||
+	  setup_order(thd, select_lex->ref_pointer_array, &tables,
+                    fields, all_fields, (ORDER*) order->first))
+    {
+      delete select;
+      free_underlaid_joins(thd, &thd->lex->select_lex);
+      DBUG_RETURN(TRUE);
+    }
+  }
+
   const_cond= (!conds || conds->const_item());
   safe_update=test(thd->options & OPTION_SAFE_UPDATES);
   if (safe_update && const_cond)
@@ -148,23 +169,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   {
     uint         length= 0;
     SORT_FIELD  *sortorder;
-    TABLE_LIST   tables;
-    List<Item>   fields;
-    List<Item>   all_fields;
     ha_rows examined_rows;
-
-    bzero((char*) &tables,sizeof(tables));
-    tables.table = table;
-    tables.alias = table_list->alias;
-
-      if (select_lex->setup_ref_array(thd, order->elements) ||
-	  setup_order(thd, select_lex->ref_pointer_array, &tables,
-                    fields, all_fields, (ORDER*) order->first))
-    {
-      delete select;
-      free_underlaid_joins(thd, &thd->lex->select_lex);
-      DBUG_RETURN(TRUE);
-    }
     
     if ((!select || table->quick_keys.is_clear_all()) && limit != HA_POS_ERROR)
       usable_index= get_index_for_order(table, (ORDER*)(order->first), limit);