更新表中的记录（如果存在）（带子句）或如果不存在则创建它

I am attempting to write a query that will update the record if it exists, or create it if it does not, however I want to do that based on the condition that text_value is not already set.

I initally thought of using REPLACE, but that does not support a WHERE clause.

REPLACE INTO settings
    SET var_name = '',
        var_group = '',
        text_value = '',
        country_id = ''

Can I do what I want to do in one query? I am trying to do so without having to write something like this where I have two queries in my PHP:

SELECT FROM settings WHERE text_value != '' AND country_id = $country_id

IF that returns no results then

INSERT INTO settings...

This is my table DDL information:

CREATE TABLE `settings` (
  `settings_id` int(11) NOT NULL auto_increment,
  `var_name` varchar(50) default NULL,
  `var_group` varchar(26) NOT NULL,
  `text_value` text NOT NULL,
  `country_id` int(11) NOT NULL,
  PRIMARY KEY  (`settings_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8