Index: src/select.c
==================================================================
--- src/select.c
+++ src/select.c
@@ -10,11 +10,11 @@
 **
 *************************************************************************
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 **
-** $Id: select.c,v 1.507 2009/04/02 16:59:47 drh Exp $
+** $Id: select.c,v 1.508 2009/04/16 00:24:24 drh Exp $
 */
 #include "sqliteInt.h"
 
 
 /*
@@ -1392,11 +1392,12 @@
   if( p->pPrior ){
     pRet = multiSelectCollSeq(pParse, p->pPrior, iCol);
   }else{
     pRet = 0;
   }
-  if( pRet==0 ){
+  assert( iCol>=0 );
+  if( pRet==0 && iCol<p->pEList->nExpr ){
     pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
   }
   return pRet;
 }
 #endif /* SQLITE_OMIT_COMPOUND_SELECT */
@@ -2099,11 +2100,11 @@
       }
     }
   }
 
   /* Compute the comparison permutation and keyinfo that is used with
-  ** the permutation in order to comparisons to determine if the next
+  ** the permutation used to determine if the next
   ** row of results comes from selectA or selectB.  Also add explicit
   ** collations to the ORDER BY clause terms so that when the subqueries
   ** to the right and the left are evaluated, they use the correct
   ** collation.
   */

Index: test/select4.test
==================================================================
--- test/select4.test
+++ test/select4.test
@@ -10,11 +10,11 @@
 #***********************************************************************
 # This file implements regression tests for SQLite library.  The
 # focus of this file is testing UNION, INTERSECT and EXCEPT operators
 # in SELECT statements.
 #
-# $Id: select4.test,v 1.29 2008/08/04 03:51:24 danielk1977 Exp $
+# $Id: select4.test,v 1.30 2009/04/16 00:24:24 drh Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 # Most tests in this file depend on compound-select. But there are a couple
@@ -372,10 +372,15 @@
     SELECT n FROM t1 WHERE log=3
     ORDER BY log;
   }} msg]
   lappend v $msg
 } {1 {SELECTs to the left and right of UNION ALL do not have the same number of result columns}}
+do_test select4-5.3-3807-1 {
+  catchsql {
+    SELECT 1 UNION SELECT 2, 3 UNION SELECT 4, 5 ORDER BY 1;
+  }
+} {1 {SELECTs to the left and right of UNION do not have the same number of result columns}}
 do_test select4-5.4 {
   set v [catch {execsql {
     SELECT log FROM t1 WHERE n=2
     UNION ALL
     SELECT log FROM t1 WHERE n=3
@@ -789,8 +794,15 @@
     EXCEPT
     SELECT x FROM t2
   }
 } {1 {SELECTs to the left and right of UNION do not have the same number of result columns}}
 
+do_test select4-12.1 {
+  sqlite3 db2 :memory:
+  catchsql {
+    SELECT 1 UNION SELECT 2,3 UNION SELECT 4,5 ORDER BY 1;
+  } db2
+} {1 {SELECTs to the left and right of UNION do not have the same number of result columns}}
+
 } ;# ifcapable compound
 
 finish_test