bug articles --mysql the sum function

The summing function is mysql sum (), for example:

<select id="getPayAmount" resultType="java.lang.Integer" parameterType="java.lang.String">
        select
        sum(oeop.PAY_AMOUNT)
        from OC_ERP_ORDER_PAY oeop
        where 1=1 
        and oeop.ERP_ORDER_ID=#{erpOrderId}
    </select>

The above is a piece of code in mybatis mapping xml file for a request to pay the sum, the receiver type with Integer, as an int in the wrapper object that can receive null if using int basic types of reception, so that when the query result is null when, it will be reported abnormal.

Mapper embodiment of correctly received

public Integer getPayAmount(String erpOrderId);

mapper may be reported to the reception in unusual ways

public int getPayAmount(String erpOrderId);

mysql in other relevant math functions, are likely to have secondary cases.