Index: lib/dml/oci_native_moodle_database.php
===================================================================
RCS file: /cvsroot/moodle/moodle/lib/dml/oci_native_moodle_database.php,v
retrieving revision 1.33
diff -u -r1.33 oci_native_moodle_database.php
--- lib/dml/oci_native_moodle_database.php	8 Nov 2009 23:13:31 -0000	1.33
+++ lib/dml/oci_native_moodle_database.php	7 Jan 2010 12:14:39 -0000
@@ -1457,9 +1457,9 @@
 
     public function sql_isempty($tablename, $fieldname, $nullablefield, $textfield) {
         if ($textfield) {
-            return " ".$this->sql_compare_text($fieldname)." = '".$this->sql_empty()."' ";
+            return " (".$this->sql_compare_text($fieldname)." = '".$this->sql_empty()."') ";
         } else {
-            return " $fieldname = '".$this->sql_empty()."' ";
+            return " ($fieldname = '".$this->sql_empty()."') ";
         }
     }
 
Index: lib/dml/mssql_native_moodle_database.php
===================================================================
RCS file: /cvsroot/moodle/moodle/lib/dml/mssql_native_moodle_database.php,v
retrieving revision 1.14
diff -u -r1.14 mssql_native_moodle_database.php
--- lib/dml/mssql_native_moodle_database.php	7 Nov 2009 08:52:57 -0000	1.14
+++ lib/dml/mssql_native_moodle_database.php	7 Jan 2010 12:14:38 -0000
@@ -1113,9 +1113,9 @@
 
    public function sql_isempty($tablename, $fieldname, $nullablefield, $textfield) {
         if ($textfield) {
-            return $this->sql_compare_text($fieldname)." = '' ";
+            return ' (' . $this->sql_compare_text($fieldname) . " = '') ";
         } else {
-            return " $fieldname = '' ";
+            return " ($fieldname = '') ";
         }
     }
 
Index: lib/dml/moodle_database.php
===================================================================
RCS file: /cvsroot/moodle/moodle/lib/dml/moodle_database.php,v
retrieving revision 1.107
diff -u -r1.107 moodle_database.php
--- lib/dml/moodle_database.php	8 Nov 2009 21:19:11 -0000	1.107
+++ lib/dml/moodle_database.php	7 Jan 2010 12:14:38 -0000
@@ -1843,7 +1843,7 @@
      * @return string the sql code to be added to check for empty values
      */
     public function sql_isempty($tablename, $fieldname, $nullablefield, $textfield) {
-        return " $fieldname = '' ";
+        return " ($fieldname = '') ";
     }
 
     /**