diff --git a/php/libraries/Database.class.inc b/php/libraries/Database.class.inc
index d86ca07de1a..90511fffc38 100644
--- a/php/libraries/Database.class.inc
+++ b/php/libraries/Database.class.inc
@@ -389,7 +389,7 @@ class Database
             $query = "INSERT INTO $table SET ";
         }
         $prepQ  = $query;
-        $query .= $this->_implodeWithKeys(', ', $set);
+        $query .= $this->_implodeWithKeys(', ', $set, 'set_');
 
         $exec_params = array();
         $prepQ      .= $this->_implodeAsPrepared(",", $set, $exec_params);
@@ -454,7 +454,7 @@ class Database
     function replace($table, $set)
     {
         $query  = "REPLACE INTO $table SET ";
-        $query .= $this->_implodeWithKeys(', ', $set);
+        $query .= $this->_implodeWithKeys(', ', $set, 'set_');
 
         if (DEBUG) {
             fwrite(STDERR, $query."\n");
@@ -531,9 +531,9 @@ class Database
          * the top of the page when showDatabaseQueries is on. It isn't
          * actually executed. */
         $query  = "UPDATE $table SET ";
-        $query .= $this->_implodeWithKeys(', ', $set);
+        $query .= $this->_implodeWithKeys(', ', $set, 'set_');
         $query .= " WHERE ";
-        $where  = $this->_implodeWithKeys(' AND ', $i_where);
+        $where  = $this->_implodeWithKeys(' AND ', $i_where, 'where_');
 
         /* This generates the version of the update statement which is
          * executed. */
@@ -590,7 +590,7 @@ class Database
     function delete($table, $where)
     {
         $query  = "DELETE FROM $table WHERE ";
-        $where  = $this->_implodeWithKeys(' AND ', $where);
+        $where  = $this->_implodeWithKeys(' AND ', $where, 'where_');
         $query .= $where;
 
         if (DEBUG) {
@@ -937,13 +937,13 @@ class Database
      * Sets each hash element into the format key='value', and then
      * implodes the resultant array with the specified glue
      *
-     * @param string               $glue      The glue to pass to php's implode
-     *                                        function
-     * @param array<string,string> $dataArray The array with keys to implode
+     * @param string $glue      The glue to pass to php's implode function
+     * @param array  $dataArray The array with keys to implode
+     * @param string $clause    The type of clause set_|where_
      *
      * @return string
      */
-    function _implodeWithKeys($glue, $dataArray)
+    function _implodeWithKeys($glue, $dataArray, $clause = 'set_')
     {
         $output = array();
         if (!is_array($dataArray) || count($dataArray)==0) {
@@ -951,8 +951,9 @@ class Database
         }
 
         foreach ($dataArray as $key => $item ) {
-            if ($item===null || $item==='') {
-                $output[] = "`$key`=NULL";
+            if (is_null($item)) {
+                $output[] = $clause == 'where_'
+                ? "`$key` IS NULL" : "`$key` = NULL";
             } else {
                 $item     = $this->quote($item);
                 $output[] = "`$key`=$item";
@@ -985,12 +986,16 @@ class Database
 
         $output = array();
         foreach ($dataArray as $key => $item ) {
-            $varname  = str_replace("%", "_percent_", $key);
-            $output[] = "`$key`=:$prefix$varname";
-            if ($exec_vals !== null) {
-                $exec_vals["$prefix$varname"] = $item;
+            $varname = str_replace("%", "_percent_", $key);
+            if (is_null($item)) {
+                $output[] = $prefix == 'where_'
+                ? "`$key` IS NULL" : "`$key` = NULL";
+            } else {
+                $output[] = "`$key`=:$prefix$varname";
+                if ($exec_vals !== null) {
+                    $exec_vals["$prefix$varname"] = $item;
+                }
             }
-
         }
         return implode($glue, $output);
     }
diff --git a/test/unittests/Database_Test.php b/test/unittests/Database_Test.php
index 4c2826fb617..5e72f765a08 100644
--- a/test/unittests/Database_Test.php
+++ b/test/unittests/Database_Test.php
@@ -73,8 +73,7 @@ function testSetFakeData() {
                 )
 
             )
-        );
-
+        ); 
     }
 
 
@@ -156,7 +155,157 @@ function testUnsafeInsertDoesntEscapeHTML() {
         $stub->unsafeinsert("test", array('field' => '<b>Hello</b>'), array());
 
     }
-}
 
+    function testDeleteWithIsNull() {
+        $this->_factory   = NDB_Factory::singleton();
+        $DB = Database::singleton();
+        $DB->setFakeTableData(
+            "ConfigSettings",
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                ),
+                1 => array(
+                    'ID' => 99992,
+                    'Name' => 'test 2',
+                    'Description' => null,
+                    'Visible' => '1'
+                )
+            )
+        );
+
+        $DB->delete("ConfigSettings", array('Visible' => 1, 'Description' => null));
+        $allSetting = $DB->pselect("SELECT ID, Name, Description, Visible FROM ConfigSettings", array());
+        $DB->run("DROP TEMPORARY TABLE ConfigSettings");
+        $this->assertEquals(
+            $allSetting,
+            array(
+                0 => array(
+                    'ID' => '99991',
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                )
+            )
+        );
+
+    } 
 
-?>
+    function testUpdateWithIsNull() {
+        $this->_factory   = NDB_Factory::singleton();
+        $DB = Database::singleton();
+        $DB->setFakeTableData(
+            "ConfigSettings",
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                ),
+                1 => array(
+                    'ID' => 99992,
+                    'Name' => 'test 2',
+                    'Description' => null,
+                    'Visible' => '1'
+                )
+            )
+        );
+        $DB->update("ConfigSettings", array('Visible' => null, 'Description' => 'new description'), array('Description' => null));
+        $allSetting = $DB->pselect("SELECT ID, Name, Description, Visible FROM ConfigSettings", array());
+        $DB->run("DROP TEMPORARY TABLE ConfigSettings");
+        $this->assertEquals(
+            $allSetting,
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                ),
+                1 => array(
+                    'ID' => 99992,
+                    'Name' => 'test 2',
+                    'Description' => 'new description',
+                    'Visible' => null
+                )
+            )
+        );
+    }
+
+    function testInsertWithIsNull() {
+        $this->_factory   = NDB_Factory::singleton();
+        $DB = Database::singleton();
+        $DB->setFakeTableData(
+            "ConfigSettings",
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                )
+            )
+        );
+        $DB->insert("ConfigSettings", array('ID' => 99992, 'Name' => 'test 2', 'Visible' => 1, 'Description' => null));
+        $allSetting = $DB->pselect("SELECT ID, Name, Description, Visible FROM ConfigSettings", array());
+        $DB->run("DROP TEMPORARY TABLE ConfigSettings");
+        $this->assertEquals(
+            $allSetting,
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                ),
+                1 => array(
+                    'ID' => 99992,
+                    'Name' => 'test 2',
+                    'Description' => null,
+                    'Visible' => '1'
+                )
+            )
+        );
+    }
+
+    function testReplaceWithIsNull() {
+        $this->_factory   = NDB_Factory::singleton();
+        $DB = Database::singleton();
+        $DB->setFakeTableData(
+            "ConfigSettings",
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => 'permanent',
+                    'Visible' => '1'
+                )
+            )
+        );
+        $DB->replace("ConfigSettings", array('ID' => 99991, 'Name' => 'test 1', 'Visible' => 1, 'Description' => null));
+        $DB->replace("ConfigSettings", array('ID' => 99992, 'Name' => 'test 2', 'Visible' => 1, 'Description' => null));
+        $allSetting = $DB->pselect("SELECT ID, Name, Description, Visible FROM ConfigSettings", array());
+        $DB->run("DROP TEMPORARY TABLE ConfigSettings");
+        $this->assertEquals(
+            $allSetting,
+            array(
+                0 => array(
+                    'ID' => 99991,
+                    'Name' => 'test 1',
+                    'Description' => null,
+                    'Visible' => '1'
+                ),
+                1 => array(
+                    'ID' => 99992,
+                    'Name' => 'test 2',
+                    'Description' => null,
+                    'Visible' => '1'
+                )
+            )
+        );
+    }
+}