mybatis select字段动态设置

@Select("SELECT IFNULL(SUM(${val}),0) cnt FROM table WHERE  DATE_FORMAT(IF (m < 10,CONCAT(y,'-0',m,'-01'),CONCAT(y,'-',m,'-01')),'%Y-%m-%d') BETWEEN ${last} AND ${cur}")
@Options(statementType = StatementType.STATEMENT)
String sumTotalByVal(@Param("last") String last,@Param("cur") String cur,@Param("val") String val);

//因为使用$ 必须把 ' 手动加进去
String cur = "'" + year + "-" + month + "-31'";
String last = "'" + year + "-01-01'";