mysql+mybatis对为null的值赋默认值（ifnull）

深藏阁楼爱情的钟 2021-09-29 01:56 1251阅读 0赞

查询两张表 并且对为空的值做默认值

select 
        u.User_pictureUrl,
        u.User_phone,u.ID as userId,
        u.user_nickname,
        IFNULL(f.userFriend_status,3)as status ,
        IFNULL(f.userFriend_comment,' ')as userFriend_comment,
        IFNULL(f.userFriend_address,' ')as userFriend_address
    from 
        tab_userinfo u 
        LEFT JOIN tab_userfriend f ON  u.ID=f.userFriend_user_id  
    where 
        u.ID=#{userId}

mybatis中插入

<insert id="insertForeach" parameterType="java.util.List" >
            insert into user_message
            (
            skip_id,user_id
            )
            values
            <foreach collection="list" item="userMessage" index="index" separator=",">
                (
                ifnull(#{userMessage.skipId},"0"),
                #{userMessage.userId}
                )
            </foreach>
    </insert>

等同于：

<if test="userMessage.skipId !=null and userMessage.skipId!=''">
    	#{userMessage.skipId},
    </if>
    <if test="userMessage.skipSonId !=null and userMessage.skipSonId!=''">
    	#{userMessage.skipSonId},
    </if>
    <if test="userMessage.jumpType !=null and userMessage.jumpType!=''">
    	#{userMessage.jumpType},
    </if>
     
     
    <if test="userMessage.skipId ==null or userMessage.skipId ==''">
    	"0",
    </if>
    <if test="userMessage.skipSonId ==null or userMessage.skipSonId ==''">
    	"0",
    </if>
    <if test="userMessage.jumpType ==null or userMessage.jumpType ==''">
    	0,
    </if>

详见：[https://blog.csdn.net/weixin\_38137028/article/details/88245042][https_blog.csdn.net_weixin_38137028_article_details_88245042]

[https_blog.csdn.net_weixin_38137028_article_details_88245042]: https://blog.csdn.net/weixin_38137028/article/details/88245042