Mysql Concat非空值
伙计,我正试图从列表列中提取非空值。 我不需要那个空值Mysql Concat非空值,mysql,Mysql,伙计,我正试图从列表列中提取非空值。 我不需要那个空值 SELECT Emp_fname, Call_number, concat( Aud_name,Mag_name,Boo_name) as name FROM manage left JOIN call_number ON manage.Man_Call_id = call_number.Call_id left JOIN book_ ON call_number.Call_id = book_.Boo_id left JOIN em
SELECT Emp_fname, Call_number, concat( Aud_name,Mag_name,Boo_name) as name
FROM manage left JOIN call_number ON manage.Man_Call_id = call_number.Call_id
left JOIN book_ ON call_number.Call_id = book_.Boo_id
left JOIN employee_ ON manage.Man_emp_id = employee_.Emp_id
left JOIN audiovisual_ ON call_number.Call_id = audiovisual_.Aud_Call_id
left join magzine_ ON call_number.Call_id = magzine_.Mag_Call_id
如果传递了一个
NULL
值,那么CONCAT
函数将返回NULL
。如果在使用列列表调用CONCAT
时要忽略可能的NULL
值,则可以使用COALESCE
。以下是一个完全忽略NULL
的查询版本:
SELECT
Emp_fname,
Call_number,
CONCAT(COALESCE(Aud_name, ''), COALESCE(Mag_name, ''), COALESCE(Boo_name, '')) AS name
FROM manage
...
如果不想用空字符串替换空字符串,可以使用任何字符串替换。请在此处添加查询。选择Emp\u fname、Call\u number、concat(Aud\u name、Mag\u name、Boo\u name)作为名称,来自manage left JOIN call\u number ON manage.Man\u call\u id=call\u number.call\u id=book\u number.Boo\u id left JOIN employee\u ON manage.Man\u emp\u id=employee\u.emp\u id left JOIN audiovisual\u number.call\u id=Aud\u id left JOIN magzine\u call\u number.call\u id=magzine\u call\u是什么你的问题,你能给我们看一些样本数据吗?什么是
Aud\u name,Mag\u name,Boo\u name
?