fix for a bug with two natural joins.

mysql-test/r/join_outer.result

@@ -652,3 +652,15 @@ fooID	barID	fooID
 20	2	NULL
 30	3	30
 drop table t1,t2;
+drop table if exists t3;
+create table t1 (i int);
+create table t2 (i int);
+create table t3 (i int);
+insert into t1 values(1),(2);
+insert into t2 values(2),(3);
+insert into t3 values(2),(4);
+select * from t1 natural left join t2 natural left join t3;
+i	i	i
+1	NULL	NULL
+2	2	2
+drop table t1,t2,t3;

mysql-test/t/join_outer.test

@@ -416,3 +416,12 @@ explain select * from t2 left join t1 on t1.fooID = t2.fooID and t1.fooID = 30;
 select * from t2 left join t1 on t1.fooID = t2.fooID and t1.fooID = 30;
 select * from t2 left join t1 ignore index(primary) on t1.fooID = t2.fooID and t1.fooID = 30;
 drop table t1,t2;
+drop table if exists t3;
+create table t1 (i int);
+create table t2 (i int);
+create table t3 (i int);
+insert into t1 values(1),(2);
+insert into t2 values(2),(3);
+insert into t3 values(2),(4);
+select * from t1 natural left join t2 natural left join t3;
+drop table t1,t2,t3;

sql/sql_yacc.yy

@@ -495,8 +495,8 @@ bool my_yyoverflow(short **a, YYSTYPE **b,int *yystacksize);
 /* These don't actually affect the way the query is really evaluated, but
    they silence a few warnings for shift/reduce conflicts. */
 %left	','
-%left	STRAIGHT_JOIN JOIN_SYM
-%nonassoc	CROSS INNER_SYM NATURAL LEFT RIGHT
+%left	STRAIGHT_JOIN JOIN_SYM NATURAL
+%nonassoc	CROSS INNER_SYM  LEFT RIGHT
 
 %type <lex_str>
 	IDENT TEXT_STRING REAL_NUM FLOAT_NUM NUM LONG_NUM HEX_NUM LEX_HOSTNAME