Mysql select语句设置默认值的方法
网络编程 2021-07-05 15:27www.168986.cn编程入门
这篇文章主要介绍了Mysql select语句设置默认值的方法,需要的朋友可以参考下
1.在没有设置默认值的情况下
SELECT userinfo.id, user_name, role, adm_regionid, region_name , create_time
FROM userinfo
LEFT JOIN region ON userinfo.adm_regionid = region.id
结果
SELECT userinfo.id, user_name, role, adm_regionid, IFNULL(region_name,0) as region_name, create_time
FROM userinfo
LEFT JOIN region ON userinfo.adm_regionid = region.id
即如果region_name一列的值为空，则显示为0，结果为
本文来自http://blog.csdn./xyw_blog/article/details/26250331
代码如下:
SELECT userinfo.id, user_name, role, adm_regionid, region_name , create_time
FROM userinfo
LEFT JOIN region ON userinfo.adm_regionid = region.id
结果
设置显示默认值
代码如下:
SELECT userinfo.id, user_name, role, adm_regionid, IFNULL(region_name,0) as region_name, create_time
FROM userinfo
LEFT JOIN region ON userinfo.adm_regionid = region.id
即如果region_name一列的值为空，则显示为0，结果为
本文来自http://blog.csdn./xyw_blog/article/details/26250331