如果任何字段包含 NULL，MySQL CONCAT 将返回 NULL

Question

我的表“设备”中有以下数据

affiliate_name  affiliate_location  model     ip             os_type    os_version 

cs1             inter               Dell     10.125.103.25   Linux      Fedora  
cs2             inter               Dell     10.125.103.26   Linux      Fedora  
cs3             inter               Dell     10.125.103.27   NULL       NULL    
cs4             inter               Dell     10.125.103.28   NULL       NULL    

我执行了以下查询

SELECT CONCAT(`affiliate_name`,'-',`model`,'-',`ip`,'-',`os_type`,'-',`os_version`) AS device_name
FROM devices

它返回下面给出的结果

cs1-Dell-10.125.103.25-Linux-Fedora
cs2-Dell-10.125.103.26-Linux-Fedora
(NULL)
(NULL)

如何解决这个问题，使其忽略 NULL 并且结果应该是

cs1-Dell-10.125.103.25-Linux-Fedora
cs2-Dell-10.125.103.26-Linux-Fedora
cs3-Dell-10.125.103.27-
cs4-Dell-10.125.103.28-

Answer 1

通过将 NULL 值包装在 COALESCE 中，将其转换为空字符串

SELECT CONCAT(COALESCE(`affiliate_name`,''),'-',COALESCE(`model`,''),'-',COALESCE(`ip`,''),'-',COALESCE(`os_type`,''),'-',COALESCE(`os_version`,'')) AS device_name
FROM devices