Bug #16076289 : BACKPORT FIX FOR BUG #14786792 TO 5.5

	
	Backport the changes for bug#14786792 which is regression 
	of fix for bug#11761854.So backported both changes.

mysql-test/r/subselect.result

@@ -4769,9 +4769,9 @@ a	1
 SELECT * FROM t1 JOIN ((SELECT 1 UNION SELECT 1)) ON 1;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')) ON 1' at line 1
 SELECT * FROM t1 JOIN  (t1 t1a UNION SELECT 1)  ON 1;
-ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ON 1' at line 1
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')  ON 1' at line 1
 SELECT * FROM t1 JOIN ((t1 t1a UNION SELECT 1)) ON 1;
-ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') ON 1' at line 1
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')) ON 1' at line 1
 SELECT * FROM t1 JOIN  (t1 t1a)  t1a ON 1;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 't1a ON 1' at line 1
 SELECT * FROM t1 JOIN ((t1 t1a)) t1a ON 1;

sql/sql_yacc.yy

@@ -773,6 +773,7 @@ static bool add_create_index (LEX *lex, Key::Keytype type,
   enum Foreign_key::fk_option m_fk_option;
   enum enum_yes_no_unknown m_yes_no_unk;
   Diag_condition_item_name diag_condition_item_name;
+  bool is_not_empty;
 }
 
 %{
@@ -1629,6 +1630,9 @@ END_OF_INPUT
         '-' '+' '*' '/' '%' '(' ')'
         ',' '!' '{' '}' '&' '|' AND_SYM OR_SYM OR_OR_SYM BETWEEN_SYM CASE_SYM
         THEN_SYM WHEN_SYM DIV_SYM MOD_SYM OR2_SYM AND_AND_SYM DELETE_SYM
+
+%type <is_not_empty> opt_union_order_or_limit
+
 %%
 
 /*
@@ -9448,10 +9452,12 @@ table_factor:
               lex->pop_context();
               lex->nest_level--;
             }
-            else if (($3->select_lex &&
-                     $3->select_lex->master_unit()->is_union()) || $5)
+            else if ($5 != NULL)
             {
-              /* simple nested joins cannot have aliases or unions */
+              /*
+                Tables with or without joins within parentheses cannot
+                have aliases, and we ruled out derived tables above.
+              */
               my_parse_error(ER(ER_SYNTAX_ERROR));
               MYSQL_YYABORT;
             }
@@ -9464,8 +9470,34 @@ table_factor:
           }
         ;
 
+/*
+  This rule accepts just about anything. The reason is that we have
+  empty-producing rules in the beginning of rules, in this case
+  subselect_start. This forces bison to take a decision which rules to
+  reduce by long before it has seen any tokens. This approach ties us
+  to a very limited class of parseable languages, and unfortunately
+  SQL is not one of them. The chosen 'solution' was this rule, which
+  produces just about anything, even complete bogus statements, for
+  instance ( table UNION SELECT 1 ).
+  Fortunately, we know that the semantic value returned by
+  select_derived is NULL if it contained a derived table, and a pointer to
+  the base table's TABLE_LIST if it was a base table. So in the rule
+  regarding union's, we throw a parse error manually and pretend it
+  was bison that did it.
+ 
+  Also worth noting is that this rule concerns query expressions in
+  the from clause only. Top level select statements and other types of
+  subqueries have their own union rules.
+*/
 select_derived_union:
           select_derived opt_union_order_or_limit
+          {
+            if ($1 && $2)
+            {
+              my_parse_error(ER(ER_SYNTAX_ERROR));
+              MYSQL_YYABORT;
+            }
+          }
         | select_derived_union
           UNION_SYM
           union_option
@@ -9482,6 +9514,13 @@ select_derived_union:
             Lex->pop_context();
           }
           opt_union_order_or_limit
+          {
+            if ($1 != NULL)
+            {
+              my_parse_error(ER(ER_SYNTAX_ERROR));
+              MYSQL_YYABORT;
+            }
+          }
         ;
 
 /* The equivalent of select_init2 for nested queries. */
@@ -13953,8 +13992,8 @@ union_opt:
         ;
 
 opt_union_order_or_limit:
-	  /* Empty */
-	| union_order_or_limit
+          /* Empty */{ $$= false; }
+	| union_order_or_limit { $$= true; }
 	;
 
 union_order_or_limit: