Make db_select() clear cached database metadata
diff --git a/system/database/drivers/sqlsrv/sqlsrv_driver.php b/system/database/drivers/sqlsrv/sqlsrv_driver.php
index 0cd9ce1..c55d5f7 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_driver.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_driver.php
@@ -171,6 +171,7 @@
 		if ($this->_execute('USE '.$this->escape_identifiers($database)))
 		{
 			$this->database = $database;
+			$this->data_cache = array();
 			return TRUE;
 		}