A fix for a crashing bug in EXPLAIN on derived tables with a join.

mysql-test/r/derived.result

@@ -105,6 +105,11 @@ a	b
 1	a
 2	b
 3	c
+explain select * from (select * from t1,t2 where t1.a=t2.a) t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	1	
+2	DERIVED	t2	system	NULL	NULL	NULL	NULL	1	
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
 drop table t1, t2;
 create table t1(a int not null, t char(8), index(a));
 SELECT * FROM (SELECT * FROM t1) as b ORDER BY a  ASC LIMIT 0,20;

mysql-test/t/derived.test

@@ -41,6 +41,7 @@ CREATE TABLE t2 (a int not null);
 insert into t2 values(1);
 select * from (select * from t1 where t1.a=(select a from t2 where t2.a=t1.a)) a;
 select * from (select * from t1 where t1.a=(select t2.a from t2 where t2.a=t1.a) union select t1.a, t1.b from t1) a;
+explain select * from (select * from t1,t2 where t1.a=t2.a) t1;
 drop table t1, t2;
 create table t1(a int not null, t char(8), index(a));
 disable_query_log;

sql/sql_derived.cc

@@ -194,7 +194,10 @@ int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit,
 	  {
 	    // to fix a problem in EXPLAIN
 	    if (tables)
-	      tables->table_list->table=tables->table;
+	    {
+	      for (TABLE_LIST *cursor= tables;  cursor;  cursor= cursor->next)
+		cursor->table_list->table=cursor->table;
+	    }
 	  }
 	  else
 	    unit->exclude_level();