diff --git a/system/database/drivers/cubrid/cubrid_driver.php b/system/database/drivers/cubrid/cubrid_driver.php
index cb33919..afdaef3 100644
--- a/system/database/drivers/cubrid/cubrid_driver.php
+++ b/system/database/drivers/cubrid/cubrid_driver.php
@@ -156,19 +156,15 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
-	 * @access	public
 	 * @return	string
 	 */
-	function _version()
+	public function version()
 	{
-		// To obtain the CUBRID Server version, no need to run the SQL query.
-		// CUBRID PHP API provides a function to determin this value.
-		// This is why we also need to add 'cubrid' value to the list of
-		// $driver_version_exceptions array in DB_driver class in
-		// version() function.
-		return cubrid_get_server_info($this->conn_id);
+		return isset($this->data_cache['version'])
+			? $this->data_cache['version']
+			: $this->data_cache['version'] = cubrid_get_server_info($this->conn_id);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/interbase/interbase_driver.php b/system/database/drivers/interbase/interbase_driver.php
index 51e814e..f4bd9e2 100644
--- a/system/database/drivers/interbase/interbase_driver.php
+++ b/system/database/drivers/interbase/interbase_driver.php
@@ -115,19 +115,24 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
 	 * @return	string
 	 */
-	protected function _version()
+	public function version()
 	{
+		if (isset($this->data_cache['version']))
+		{
+			return $this->data_cache['version'];
+		}
+
 		if (($service = ibase_service_attach($this->hostname, $this->username, $this->password)))
 		{
-			$version = ibase_server_info($service, IBASE_SVC_SERVER_VERSION);
+			$this->data_cache['version'] = ibase_server_info($service, IBASE_SVC_SERVER_VERSION);
 
 			// Don't keep the service open
 			ibase_service_detach($service);
-			return $version;
+			return $this->data_cache['version'];
 		}
 
 		return FALSE;
@@ -581,7 +586,7 @@
 		$orig_sql = $sql;
 
 		// Limit clause depends on if Interbase or Firebird
-		if (stripos($this->_version(), 'firebird') !== FALSE)
+		if (stripos($this->version(), 'firebird') !== FALSE)
 		{
 			$sql = 'FIRST '. (int) $limit;
 
diff --git a/system/database/drivers/mssql/mssql_driver.php b/system/database/drivers/mssql/mssql_driver.php
index 188c91f..147c634 100644
--- a/system/database/drivers/mssql/mssql_driver.php
+++ b/system/database/drivers/mssql/mssql_driver.php
@@ -339,12 +339,11 @@
 	/**
 	* Version number query string
 	*
-	* @access public
-	* @return string
+	* @return	string
 	*/
-	function _version()
+	protected function _version()
 	{
-		return "SELECT @@VERSION AS ver";
+		return 'SELECT @@VERSION AS ver';
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/mysql/mysql_driver.php b/system/database/drivers/mysql/mysql_driver.php
index a7f08d1..7108a6d 100644
--- a/system/database/drivers/mysql/mysql_driver.php
+++ b/system/database/drivers/mysql/mysql_driver.php
@@ -157,13 +157,15 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
 	 * @return	string
 	 */
-	protected function _version()
+	public function version()
 	{
-		return 'SELECT version() AS ver';
+		return isset($this->data_cache['version'])
+			? $this->data_cache['version']
+			: $this->data_cache['version'] = @mysql_get_server_info($this->conn_id);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index 0313713..1935394 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -157,13 +157,15 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
 	 * @return	string
 	 */
-	protected function _version()
+	public function version()
 	{
-		return @mysqli_get_server_info($this->conn_id);
+		return isset($this->data_cache['version'])
+			? $this->data_cache['version']
+			: $this->data_cache['version'] = @mysqli_get_server_info($this->conn_id);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index 97efb46..35cafff 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -139,14 +139,15 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
-	 * @access  protected
-	 * @return  string
+	 * @return	string
 	 */
-	protected function _version()
+	public function version()
 	{
-		return oci_server_version($this->conn_id);
+		return isset($this->data_cache['version'])
+			? $this->data_cache['version']
+			: $this->data_cache['version'] = oci_server_version($this->conn_id);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/odbc/odbc_driver.php b/system/database/drivers/odbc/odbc_driver.php
index 5a93f7c..779b0c6 100644
--- a/system/database/drivers/odbc/odbc_driver.php
+++ b/system/database/drivers/odbc/odbc_driver.php
@@ -124,19 +124,6 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
-	 *
-	 * @access	public
-	 * @return	string
-	 */
-	function _version()
-	{
-		return "SELECT version() AS ver";
-	}
-
-	// --------------------------------------------------------------------
-
-	/**
 	 * Execute the query
 	 *
 	 * @access	private called by the base class
diff --git a/system/database/drivers/pdo/pdo_driver.php b/system/database/drivers/pdo/pdo_driver.php
index de5e1f0..8fdfd58 100644
--- a/system/database/drivers/pdo/pdo_driver.php
+++ b/system/database/drivers/pdo/pdo_driver.php
@@ -289,13 +289,15 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
 	 * @return	string
 	 */
-	protected function _version()
+	public function version()
 	{
-		return $this->conn_id->getAttribute(PDO::ATTR_SERVER_VERSION);
+		return isset($this->data_cache['version'])
+			? $this->data_cache['version']
+			: $this->data_cache['version'] = $this->conn_id->getAttribute(PDO::ATTR_SERVER_VERSION);
 	}
 
 	// --------------------------------------------------------------------
@@ -499,7 +501,7 @@
 	 */
 	public function insert_id($name = NULL)
 	{
-		if ($this->pdodriver === 'pgsql' && $name === NULL && $this->_version() >= '8.1')
+		if ($this->pdodriver === 'pgsql' && $name === NULL && $this->version() >= '8.1')
 		{
 			$query = $this->query('SELECT LASTVAL() AS ins_id');
 			$query = $query->row();
diff --git a/system/database/drivers/postgre/postgre_driver.php b/system/database/drivers/postgre/postgre_driver.php
index 0fcd954..d668108 100644
--- a/system/database/drivers/postgre/postgre_driver.php
+++ b/system/database/drivers/postgre/postgre_driver.php
@@ -147,14 +147,30 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
-	 * @access	public
 	 * @return	string
 	 */
-	function _version()
+	public function version()
 	{
-		return "SELECT version() AS ver";
+		if (isset($this->data_cache['version']))
+		{
+			return $this->data_cache['version'];
+		}
+
+		if (($pg_version = pg_version($this->conn_id)) === FALSE)
+		{
+			return FALSE;
+		}
+
+		/* If PHP was compiled with PostgreSQL lib versions earlier
+		 * than 7.4, pg_version() won't return the server version
+		 * and so we'll have to fall back to running a query in
+		 * order to get it.
+		 */
+		return isset($pg_version['server'])
+			? $this->data_cache['version'] = $pg_version['server']
+			: parent::version();
 	}
 
 	// --------------------------------------------------------------------
@@ -323,8 +339,7 @@
 	 */
 	function insert_id()
 	{
-		$v = $this->_version();
-		$v = $v['server'];
+		$v = $this->version();
 
 		$table	= func_num_args() > 0 ? func_get_arg(0) : NULL;
 		$column	= func_num_args() > 1 ? func_get_arg(1) : NULL;
diff --git a/system/database/drivers/sqlite/sqlite_driver.php b/system/database/drivers/sqlite/sqlite_driver.php
index 3e4b373..3eaec94 100644
--- a/system/database/drivers/sqlite/sqlite_driver.php
+++ b/system/database/drivers/sqlite/sqlite_driver.php
@@ -141,14 +141,15 @@
 	// --------------------------------------------------------------------
 
 	/**
-	 * Version number query string
+	 * Database version number
 	 *
-	 * @access	public
 	 * @return	string
 	 */
-	function _version()
+	public function version()
 	{
-		return sqlite_libversion();
+		return isset($this->data_cache['version'])
+			? $this->data_cache['version']
+			: $this->data_cache['version'] = sqlite_libversion();
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/sqlite/sqlite_forge.php b/system/database/drivers/sqlite/sqlite_forge.php
index 2b723be..fd0f3eb 100644
--- a/system/database/drivers/sqlite/sqlite_forge.php
+++ b/system/database/drivers/sqlite/sqlite_forge.php
@@ -89,7 +89,7 @@
 		$sql = 'CREATE TABLE ';
 
 		// IF NOT EXISTS added to SQLite in 3.3.0
-		if ($if_not_exists === TRUE && version_compare($this->db->_version(), '3.3.0', '>=') === TRUE)
+		if ($if_not_exists === TRUE && version_compare($this->db->version(), '3.3.0', '>=') === TRUE)
 		{
 			$sql .= 'IF NOT EXISTS ';
 		}
@@ -274,4 +274,4 @@
 }
 
 /* End of file sqlite_forge.php */
-/* Location: ./system/database/drivers/sqlite/sqlite_forge.php */
\ No newline at end of file
+/* Location: ./system/database/drivers/sqlite/sqlite_forge.php */
diff --git a/system/database/drivers/sqlsrv/sqlsrv_driver.php b/system/database/drivers/sqlsrv/sqlsrv_driver.php
index 03d7c71..5c90cb4 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_driver.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_driver.php
@@ -317,15 +317,23 @@
 	// --------------------------------------------------------------------
 
 	/**
-	* Version number query string
-	*
-	* @access public
-	* @return string
-	*/
-	function _version()
+	 * Database version number
+	 *
+	 * @return	string
+	 */
+	public function version()
 	{
-		$info = sqlsrv_server_info($this->conn_id);
-		return sprintf("select '%s' as ver", $info['SQLServerVersion']);
+		if (isset($this->data_cache['version']))
+		{
+			return $this->data_cache['version'];
+		}
+
+		if (($info = sqlsrv_server_info($this->conn_id)) === FALSE)
+		{
+			return FALSE;
+		}
+
+		return $this->data_cache['version'] = $info['SQLServerVersion'];
 	}
 
 	// --------------------------------------------------------------------