使用trim标签 suffixOverrides的作用是最后一条去掉逗号 if个就是条件判断

<update id="updateUser" parameterType="com.zy.entity.User">

UPDATE user
<trim prefix="set" suffixOverrides=",">

<if test="userName!=null">userName=#{userName},</if>

<if test="nickName!=null">nickName=#{nickName},</if>

<if test="avatar!=null">avatar=#{avatar},</if>

<if test="email!=null">email=#{email},</if>

<if test="age!=null">age=#{age},</if>

<if test="introduction!=null">introduction=#{introduction},</if>
</trim>

WHERE id=#{id}

</update>

mapper里面修改sql 如果参数为空不修改