[Mybatis]查询Sql得到一个字符串

// find min date
HashMap<String, String> minDateMap = new HashMap<String, String>();
minDateMap.put("tableName", tableName);
String minDate = session.selectOne("findMinDate", minDateMap);

xml中写

<!-- SweepawayExpiredDataJob -->
<select id="findMinDate" resultType="java.lang.String" parameterType="java.util.HashMap">
select min(to_char(created_datetime,'yyyy-MM-dd')) from ${tableName} where created_user='user'
</select>

--END-- 2019-10-10