diff --git a/lib/datalib.php b/lib/datalib.php
index 9d257480060..c9f096af696 100644
--- a/lib/datalib.php
+++ b/lib/datalib.php
@@ -190,6 +190,95 @@ function search_users($courseid, $groupid, $searchtext, $sort='', array $excepti
     }
 }
 
+/**
+ * Returns SQL used to search through user table to find users (in a query
+ * which may also join and apply other conditions).
+ *
+ * You can combine this SQL with an existing query by adding 'AND $sql' to the
+ * WHERE clause of your query (where $sql is the first element in the array
+ * returned by this function), and merging in the $params array to the parameters
+ * of your query (where $params is the second element). Your query should use
+ * named parameters such as :param, rather than the question mark style.
+ *
+ * There are examples of basic usage in the unit test for this function.
+ *
+ * @param string $search the text to search for (empty string = find all)
+ * @param string $u the table alias for the user table in the query being
+ *     built. May be ''.
+ * @param bool $searchanywhere If true (default), searches in the middle of
+ *     names, otherwise only searches at start
+ * @param array $extrafields Array of extra user fields to include in search
+ * @param array $exclude Array of user ids to exclude (empty = don't exclude)
+ * @param array $includeonly If specified, only returns users that have ids
+ *     incldued in this array (empty = don't restrict)
+ * @return array an array with two elements, a fragment of SQL to go in the
+ *     where clause the query, and an associative array containing any required
+ *     parameters (using named placeholders).
+ */
+function users_search_sql($search, $u = 'u', $searchanywhere = true, array $extrafields = array(),
+        array $exclude = array(), array $includeonly = array()) {
+    global $DB, $CFG;
+    $params = array();
+    $tests = array();
+
+    if ($u) {
+        $u .= '.';
+    }
+
+    // If we have a $search string, put a field LIKE '$search%' condition on each field.
+    if ($search) {
+        $conditions = array(
+            $DB->sql_fullname($u . 'firstname', $u . 'lastname'),
+            $conditions[] = $u . 'lastname'
+        );
+        foreach ($extrafields as $field) {
+            $conditions[] = $u . $field;
+        }
+        if ($searchanywhere) {
+            $searchparam = '%' . $search . '%';
+        } else {
+            $searchparam = $search . '%';
+        }
+        $i = 0;
+        foreach ($conditions as $key => $condition) {
+            $conditions[$key] = $DB->sql_like($condition, ":con{$i}00", false, false);
+            $params["con{$i}00"] = $searchparam;
+            $i++;
+        }
+        $tests[] = '(' . implode(' OR ', $conditions) . ')';
+    }
+
+    // Add some additional sensible conditions.
+    $tests[] = $u . "id <> :guestid";
+    $params['guestid'] = $CFG->siteguest;
+    $tests[] = $u . 'deleted = 0';
+    $tests[] = $u . 'confirmed = 1';
+
+    // If we are being asked to exclude any users, do that.
+    if (!empty($exclude)) {
+        list($usertest, $userparams) = $DB->get_in_or_equal($exclude, SQL_PARAMS_NAMED, 'ex', false);
+        $tests[] = $u . 'id ' . $usertest;
+        $params = array_merge($params, $userparams);
+    }
+
+    // If we are validating a set list of userids, add an id IN (...) test.
+    if (!empty($includeonly)) {
+        list($usertest, $userparams) = $DB->get_in_or_equal($includeonly, SQL_PARAMS_NAMED, 'val');
+        $tests[] = $u . 'id ' . $usertest;
+        $params = array_merge($params, $userparams);
+    }
+
+    // In case there are no tests, add one result (this makes it easier to combine
+    // this with an existing query as you can always add AND $sql).
+    if (empty($tests)) {
+        $tests[] = '1 = 1';
+    }
+
+    // Combing the conditions and return.
+    return array(implode(' AND ', $tests), $params);
+}
+
+
 /**
  * This function generates the standard ORDER BY clause for use when generating
  * lists of users. If you don't have a reason to use a different order, then
diff --git a/lib/tests/datalib_test.php b/lib/tests/datalib_test.php
index e758c74f857..cce2090f444 100644
--- a/lib/tests/datalib_test.php
+++ b/lib/tests/datalib_test.php
@@ -43,6 +43,121 @@ class datalib_testcase extends advanced_testcase {
         $this->assertEquals($this->normalise_sql($expected), $this->normalise_sql($actual));
     }
 
+    /**
+     * Do a test of the user search SQL with database users.
+     */
+    public function test_users_search_sql() {
+        global $DB;
+
+        // Set up test users.
+        $this->resetAfterTest(true);
+        $user1 = array(
+            'username' => 'usernametest1',
+            'idnumber' => 'idnumbertest1',
+            'firstname' => 'First Name User Test 1',
+            'lastname' => 'Last Name User Test 1',
+            'email' => 'usertest1@email.com',
+            'address' => '2 Test Street Perth 6000 WA',
+            'phone1' => '01010101010',
+            'phone2' => '02020203',
+            'icq' => 'testuser1',
+            'skype' => 'testuser1',
+            'yahoo' => 'testuser1',
+            'aim' => 'testuser1',
+            'msn' => 'testuser1',
+            'department' => 'Department of user 1',
+            'institution' => 'Institution of user 1',
+            'description' => 'This is a description for user 1',
+            'descriptionformat' => FORMAT_MOODLE,
+            'city' => 'Perth',
+            'url' => 'http://moodle.org',
+            'country' => 'au'
+            );
+        $user1 = self::getDataGenerator()->create_user($user1);
+        $user2 = array(
+            'username' => 'usernametest2',
+            'idnumber' => 'idnumbertest2',
+            'firstname' => 'First Name User Test 2',
+            'lastname' => 'Last Name User Test 2',
+            'email' => 'usertest2@email.com',
+            'address' => '222 Test Street Perth 6000 WA',
+            'phone1' => '01010101010',
+            'phone2' => '02020203',
+            'icq' => 'testuser1',
+            'skype' => 'testuser1',
+            'yahoo' => 'testuser1',
+            'aim' => 'testuser1',
+            'msn' => 'testuser1',
+            'department' => 'Department of user 2',
+            'institution' => 'Institution of user 2',
+            'description' => 'This is a description for user 2',
+            'descriptionformat' => FORMAT_MOODLE,
+            'city' => 'Perth',
+            'url' => 'http://moodle.org',
+            'country' => 'au'
+            );
+        $user2 = self::getDataGenerator()->create_user($user2);
+
+        // Search by name (anywhere in text).
+        list($sql, $params) = users_search_sql('User Test 2', '');
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertFalse(array_key_exists($user1->id, $results));
+        $this->assertTrue(array_key_exists($user2->id, $results));
+
+        // Search by (most of) full name.
+        list($sql, $params) = users_search_sql('First Name User Test 2 Last Name User', '');
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertFalse(array_key_exists($user1->id, $results));
+        $this->assertTrue(array_key_exists($user2->id, $results));
+
+        // Search by name (start of text) valid or not.
+        list($sql, $params) = users_search_sql('User Test 2', '', false);
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertEquals(0, count($results));
+        list($sql, $params) = users_search_sql('First Name User Test 2', '', false);
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertFalse(array_key_exists($user1->id, $results));
+        $this->assertTrue(array_key_exists($user2->id, $results));
+
+        // Search by extra fields included or not (address).
+        list($sql, $params) = users_search_sql('Test Street', '', true);
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertEquals(0, count($results));
+        list($sql, $params) = users_search_sql('Test Street', '', true, array('address'));
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertEquals(2, count($results));
+
+        // Exclude user.
+        list($sql, $params) = users_search_sql('User Test', '', true, array(), array($user1->id));
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertFalse(array_key_exists($user1->id, $results));
+        $this->assertTrue(array_key_exists($user2->id, $results));
+
+        // Include only user.
+        list($sql, $params) = users_search_sql('User Test', '', true, array(), array(), array($user1->id));
+        $results = $DB->get_records_sql("SELECT id FROM {user} WHERE $sql ORDER BY username", $params);
+        $this->assertTrue(array_key_exists($user1->id, $results));
+        $this->assertFalse(array_key_exists($user2->id, $results));
+
+        // Join with another table and use different prefix.
+        set_user_preference('amphibian', 'frog', $user1);
+        set_user_preference('amphibian', 'salamander', $user2);
+        list($sql, $params) = users_search_sql('User Test 1', 'qq');
+        $results = $DB->get_records_sql("
+                SELECT
+                    up.id, up.value
+                FROM
+                    {user} qq
+                    JOIN {user_preferences} up ON up.userid = qq.id
+                WHERE
+                    up.name = :prefname
+                    AND $sql", array_merge(array('prefname' => 'amphibian'), $params));
+        $this->assertEquals(1, count($results));
+        foreach ($results as $record) {
+            $this->assertEquals('frog', $record->value);
+        }
+    }
+
     public function test_users_order_by_sql_simple() {
         list($sort, $params) = users_order_by_sql();
         $this->assert_same_sql('lastname, firstname, id', $sort);
diff --git a/user/selector/lib.php b/user/selector/lib.php
index 18e9dfc5b35..1483f6f8276 100644
--- a/user/selector/lib.php
+++ b/user/selector/lib.php
@@ -434,63 +434,8 @@ abstract class user_selector_base {
      *      this uses ? style placeholders.
      */
     protected function search_sql($search, $u) {
-        global $DB, $CFG;
-        $params = array();
-        $tests = array();
-
-        if ($u) {
-            $u .= '.';
-        }
-
-        // If we have a $search string, put a field LIKE '$search%' condition on each field.
-        if ($search) {
-            $conditions = array(
-                $DB->sql_fullname($u . 'firstname', $u . 'lastname'),
-                $conditions[] = $u . 'lastname'
-            );
-            foreach ($this->extrafields as $field) {
-                $conditions[] = $u . $field;
-            }
-            if ($this->searchanywhere) {
-                $searchparam = '%' . $search . '%';
-            } else {
-                $searchparam = $search . '%';
-            }
-            $i = 0;
-            foreach ($conditions as $key=>$condition) {
-                $conditions[$key] = $DB->sql_like($condition, ":con{$i}00", false, false);
-                $params["con{$i}00"] = $searchparam;
-                $i++;
-            }
-            $tests[] = '(' . implode(' OR ', $conditions) . ')';
-        }
-
-        // Add some additional sensible conditions
-        $tests[] = $u . "id <> :guestid";
-        $params['guestid'] = $CFG->siteguest;
-        $tests[] = $u . 'deleted = 0';
-        $tests[] = $u . 'confirmed = 1';
-
-        // If we are being asked to exclude any users, do that.
-        if (!empty($this->exclude)) {
-            list($usertest, $userparams) = $DB->get_in_or_equal($this->exclude, SQL_PARAMS_NAMED, 'ex', false);
-            $tests[] = $u . 'id ' . $usertest;
-            $params = array_merge($params, $userparams);
-        }
-
-        // If we are validating a set list of userids, add an id IN (...) test.
-        if (!empty($this->validatinguserids)) {
-            list($usertest, $userparams) = $DB->get_in_or_equal($this->validatinguserids, SQL_PARAMS_NAMED, 'val');
-            $tests[] = $u . 'id ' . $usertest;
-            $params = array_merge($params, $userparams);
-        }
-
-        if (empty($tests)) {
-            $tests[] = '1 = 1';
-        }
-
-        // Combing the conditions and return.
-        return array(implode(' AND ', $tests), $params);
+        return users_search_sql($search, 'u', $this->searchanywhere, $this->extrafields,
+                $this->exclude, $this->validatinguserids);
     }
 
     /**