Bug#58970 Problem Subquery (without referencing a table)

          and Order By
      
When having a UNION statement in a subquery, with no
referenced tables (or only a reference to the virtual
table 'dual'), the UNION did not allow an ORDER BY clause.
      
      i.e:
          SELECT(SELECT 1 AS a UNION 
                 SELECT 0 AS a 
                 ORDER BY a) AS b  or
          SELECT(SELECT 1 AS a FROM dual UNION 
                 SELECT 0 as a 
                 ORDER BY a) AS b
      
      
In addition, an ORDER BY / LIMIT clause was not accepted
in subqueries even for single SELECT statements with no 
referenced tables (or with 'dual' as table reference)
      
   i.e: 
      SELECT(SELECT 1 AS a ORDER BY a) AS b  or
      SELECT(SELECT 1 AS a FROM dual ORDER BY a) AS b
      
The fix was to allow an optional ORDER BY/LIMIT clause to
the grammar for these cases.
      
See also: Bug#57986

mysql-test/r/union.result

@@ -1744,3 +1744,28 @@ ORDER BY c2 DESC, c1 ASC LIMIT 1
 c1	c2
 t1a	3
 DROP TABLE t1, t2;
+#
+# Bug #58970 Problem Subquery (without referencing a table) 
+#            and Order By
+#
+SELECT(SELECT 0 AS a UNION SELECT 1 AS a ORDER BY a ASC  LIMIT 1) AS dev;
+dev
+0
+SELECT(SELECT 0 AS a UNION SELECT 1 AS a ORDER BY a DESC LIMIT 1) AS dev;
+dev
+1
+SELECT(SELECT 0 AS a FROM dual UNION SELECT 1 AS a FROM dual ORDER BY a ASC  LIMIT 1) AS dev;
+dev
+0
+SELECT(SELECT 0 AS a FROM dual UNION SELECT 1 AS a FROM dual ORDER BY a DESC LIMIT 1) AS dev;
+dev
+1
+SELECT(SELECT 1 AS a ORDER BY a) AS dev;
+dev
+1
+SELECT(SELECT 1 AS a LIMIT 1) AS dev;
+dev
+1
+SELECT(SELECT 1 AS a FROM dual ORDER BY a DESC LIMIT 1) AS dev;
+dev
+1

mysql-test/t/union.test

@@ -1171,3 +1171,16 @@ SELECT c1, c2 FROM (
 ) AS res;
 
 DROP TABLE t1, t2;
+
+--echo #
+--echo # Bug #58970 Problem Subquery (without referencing a table) 
+--echo #            and Order By
+--echo #
+
+SELECT(SELECT 0 AS a UNION SELECT 1 AS a ORDER BY a ASC  LIMIT 1) AS dev;
+SELECT(SELECT 0 AS a UNION SELECT 1 AS a ORDER BY a DESC LIMIT 1) AS dev;
+SELECT(SELECT 0 AS a FROM dual UNION SELECT 1 AS a FROM dual ORDER BY a ASC  LIMIT 1) AS dev;
+SELECT(SELECT 0 AS a FROM dual UNION SELECT 1 AS a FROM dual ORDER BY a DESC LIMIT 1) AS dev;
+SELECT(SELECT 1 AS a ORDER BY a) AS dev;
+SELECT(SELECT 1 AS a LIMIT 1) AS dev;
+SELECT(SELECT 1 AS a FROM dual ORDER BY a DESC LIMIT 1) AS dev;

sql/sql_yacc.yy

@@ -13914,7 +13914,7 @@ query_specification:
         ;
 
 query_expression_body:
-          query_specification
+          query_specification opt_union_order_or_limit
         | query_expression_body
           UNION_SYM union_option 
           {
@@ -13922,6 +13922,7 @@ query_expression_body:
               MYSQL_YYABORT;
           }
           query_specification
+          opt_union_order_or_limit
           {
             Lex->pop_context();
             $$= $1;