Monty, your comments ??

mysql-test/t/union.test:
  A test case for :
  
  CREATE TABLE .. SELECT .... UNION SELECT ... UNION SELECT .....
  
  and
  
  INSERT INTO ... SELECT .... UNION SELECT ... UNION SELECT ....
  
  Monty, please let me know what changes do you want me to make. 
  I could not make both in the same function, as insert requires
  that table is open.
  
  Let me know what changes to make before I plunge into:
  
  EXPLAIN SELECT ... UNION ... SELECT ......

mysql-test/t/union.test

@@ -2,7 +2,7 @@
 # Test of unions
 #
 
-drop table if exists t1,t2;
+drop table if exists t1,t2,t3;
 CREATE TABLE t1 (a int not null, b char (10) not null);
 insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
 CREATE TABLE t2 (a int not null, b char (10) not null);
@@ -25,5 +25,6 @@ select a,b from t1 into outfile 'skr' union select a,b from t2;
 select a,b from t1 order by a union select a,b from t2;
 --error 1215
 select a,b from t1 union select a from t2;
-
-drop table t1,t2;
+create table t3 select a,b from t1 union all select a,b from t2;
+insert into t3 select a,b from t1 union all select a,b from t2;
+drop table t1,t2,t3;