修改下面mybatis语句 select <choose> <when test="laborCostCity != null and laborCostCity !='' and serveCostType == null and serveCostType !=''"> ${laborCostCity} as laborCost,${serveCostType} as serveCost </when> </choose> from t_grading_new where `rank`=#{rank} and delFlag =0

根据你的需求，我修改了下面的MyBatis语句：

<select>
    <choose>
        <when test="laborCostCity != null and laborCostCity !='' and serveCostType != null and serveCostType !=''">
            SELECT ${laborCostCity} AS laborCost, ${serveCostType} AS serveCost
        </when>
        <otherwise>
            SELECT laborCost, serveCost
        </otherwise>
    </choose>
    FROM t_grading_new
    WHERE `rank` = #{rank}
    AND delFlag = 0
</select>

这个语句可以根据条件动态选择要查询的字段，如果`laborCostCity`和`serveCostType`都非空，则查询这两个字段。否则，查询全部字段`laborCost`和`serveCost`。同时，筛选出`rank`等于参数`#{rank}`并且`delFlag`等于0的记录。