Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -20,11 +20,11 @@
 **     creating ID lists
 **     BEGIN TRANSACTION
 **     COMMIT
 **     ROLLBACK
 **
-** $Id: build.c,v 1.555 2009/07/01 14:56:40 danielk1977 Exp $
+** $Id: build.c,v 1.556 2009/07/01 16:12:08 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
 /*
 ** This routine is called when a new SQL statement is beginning to
@@ -3206,31 +3206,36 @@
   Expr *pOn,              /* The ON clause of a join */
   IdList *pUsing          /* The USING clause of a join */
 ){
   struct SrcList_item *pItem;
   sqlite3 *db = pParse->db;
+  if( !p && (pOn || pUsing) ){
+    sqlite3ErrorMsg(pParse, "a JOIN clause is required before %s", 
+      (pOn ? "ON" : "USING")
+    );
+    goto append_from_error;
+  }
   p = sqlite3SrcListAppend(db, p, pTable, pDatabase);
   if( p==0 || NEVER(p->nSrc==0) ){
-    sqlite3ExprDelete(db, pOn);
-    sqlite3IdListDelete(db, pUsing);
-    sqlite3SelectDelete(db, pSubquery);
-    return p;
+    goto append_from_error;
   }
   pItem = &p->a[p->nSrc-1];
   assert( pAlias!=0 );
   if( pAlias->n ){
     pItem->zAlias = sqlite3NameFromToken(db, pAlias);
   }
   pItem->pSelect = pSubquery;
-  if( p->nSrc>1 ){
-    pItem->pOn = pOn;
-    pItem->pUsing = pUsing;
-  }else{
-    sqlite3ExprDelete(db, pOn);
-    sqlite3IdListDelete(db, pUsing);
-  }
+  pItem->pOn = pOn;
+  pItem->pUsing = pUsing;
   return p;
+
+ append_from_error:
+  assert( p==0 );
+  sqlite3ExprDelete(db, pOn);
+  sqlite3IdListDelete(db, pUsing);
+  sqlite3SelectDelete(db, pSubquery);
+  return 0;
 }
 
 /*
 ** Add an INDEXED BY or NOT INDEXED clause to the most recently added 
 ** element of the source-list passed as the second argument.

Index: test/join.test
==================================================================
--- test/join.test
+++ test/join.test
@@ -10,11 +10,11 @@
 #***********************************************************************
 # This file implements regression tests for SQLite library.
 #
 # This file implements tests for joins, including outer joins.
 #
-# $Id: join.test,v 1.26 2008/12/05 00:00:07 drh Exp $
+# $Id: join.test,v 1.27 2009/07/01 16:12:08 danielk1977 Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 do_test join-1.1 {
@@ -307,14 +307,12 @@
   catchsql {
     SELECT * FROM t1 JOIN t2 USING(d);
   }
 } {1 {cannot join using column d - column not present in both tables}}
 do_test join-3.5 {
-  catchsql {
-    SELECT * FROM t1 USING(a);
-  }
-} {0 {1 2 3 2 3 4 3 4 5}}
+  catchsql { SELECT * FROM t1 USING(a) }
+} {1 {a JOIN clause is required before USING}}
 do_test join-3.6 {
   catchsql {
     SELECT * FROM t1 JOIN t2 ON t3.a=t2.b;
   }
 } {1 {no such column: t3.a}}

Index: test/tkt3935.test
==================================================================
--- test/tkt3935.test
+++ test/tkt3935.test
@@ -10,11 +10,11 @@
 #***********************************************************************
 # This file implements regression tests for SQLite library.
 #
 # This file implements tests to verify that ticket #3935 has been fixed.
 #
-# $Id: tkt3935.test,v 1.1 2009/07/01 14:56:41 danielk1977 Exp $
+# $Id: tkt3935.test,v 1.2 2009/07/01 16:12:08 danielk1977 Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 do_test tkt3935.1 {
@@ -31,24 +31,27 @@
   execsql { SELECT j1.b FROM (t1 INNER JOIN t2 ON a=c) AS j1 }
 } {}
 
 
 do_test tkt3935.4 {
-  execsql { SELECT a FROM (t1) AS t ON b USING(a) }
-} {}
+  catchsql { SELECT a FROM (t1) AS t ON b USING(a) }
+} {1 {a JOIN clause is required before ON}}
 do_test tkt3935.5 {
-  execsql { SELECT a FROM (t1) AS t ON b }
-} {}
+  catchsql { SELECT a FROM (t1) AS t ON b }
+} {1 {a JOIN clause is required before ON}}
 do_test tkt3935.6 {
-  execsql { SELECT a FROM (SELECT * FROM t1) AS t ON b USING(a) }
-} {}
+  catchsql { SELECT a FROM (SELECT * FROM t1) AS t ON b USING(a) }
+} {1 {a JOIN clause is required before ON}}
 do_test tkt3935.7 {
-  execsql { SELECT a FROM (SELECT * FROM t1) AS t ON b }
-} {}
+  catchsql { SELECT a FROM (SELECT * FROM t1) AS t ON b }
+} {1 {a JOIN clause is required before ON}}
 do_test tkt3935.8 {
-  execsql { SELECT a FROM t1 AS t ON b }
-} {}
+  catchsql { SELECT a FROM t1 AS t ON b }
+} {1 {a JOIN clause is required before ON}}
 do_test tkt3935.9 {
-  execsql { SELECT a FROM t1 AS t ON b USING(a) }
-} {}
+  catchsql { SELECT a FROM t1 AS t ON b USING(a) }
+} {1 {a JOIN clause is required before ON}}
+do_test tkt3935.10 {
+  catchsql { SELECT a FROM t1 AS t USING(a) }
+} {1 {a JOIN clause is required before USING}}
 
 finish_test

Index: test/vtab6.test
==================================================================
--- test/vtab6.test
+++ test/vtab6.test
@@ -12,11 +12,11 @@
 #
 # This file implements tests for joins, including outer joins involving
 # virtual tables. The test cases in this file are copied from the file
 # join.test, and some of the comments still reflect that.
 #
-# $Id: vtab6.test,v 1.4 2008/07/12 14:52:21 drh Exp $
+# $Id: vtab6.test,v 1.5 2009/07/01 16:12:08 danielk1977 Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 ifcapable !vtab {
@@ -263,14 +263,12 @@
   catchsql {
     SELECT * FROM t1 JOIN t2 USING(a);
   }
 } {1 {cannot join using column a - column not present in both tables}}
 do_test vtab6-3.5 {
-  catchsql {
-    SELECT * FROM t1 USING(a);
-  }
-} {0 {1 2 3 2 3 4 3 4 5}}
+  catchsql { SELECT * FROM t1 USING(a) }
+} {1 {a JOIN clause is required before USING}}
 do_test vtab6-3.6 {
   catchsql {
     SELECT * FROM t1 JOIN t2 ON t3.a=t2.b;
   }
 } {1 {no such column: t3.a}}