Mapper.xml中新增数据并返回主键ID(MYSQL)

（一）主键为INT类型且自动增长

 <!-- useGeneratedKeys默认为false，keyProperty="数据库中的主键字段名对应的实体类字段名" -->
 <insert id="addOrders" parameterType="com.qfedu.entity.Orders" useGeneratedKeys="true" keyProperty="oid">
        insert into orders values(null,#{userId},now(),#{totalPrice},0,0)
 </insert>

（二）主键为String类型且使用UUID做为主键

 <insert id="addOrders" parameterType="com.qfedu.entity.Orders">
        <selectKey keyColumn="oid" resultType="java.lang.String" keyProperty="oid" order="BEFORE">
            SELECT replace(uuid(),'-','')
        </selectKey>
        insert into orders values(#{oid},#{userId},now(),#{totalPrice},0,0)
    </insert>