尝试根据条件获取值时出错的MYSQL案例

Question

为什么我收到此查询错误？有什么我想念的吗？

所以如果“via”字段为 O，我想获取 online_date，然后如果“via”字段为 M，我想获取 manual_date

SELECT a.seqreq,
b.idfieldb ,
c.idfieldc ,
a.number_given,
case upper(a.via) when 'O' then 'Online'
when 'O' then 'Online'
when 'M' then 'Manual'
else a.via
end as via,
case when upper(a.via) when 'O' then a.online_date
when 'M' then a.manual_date //it says error on this line ?
else a.others_date
end as date_registered
from mytablea a 
left join tbl_b b on a.idfielda=b.idfieldb
left join tbl_c c on a.idfielda=c.idfieldc
left join tbl_d d on a.userEntry=d.NoIdUser

错误信息：

W (1): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'when 'O' then

Answer 1

查询中有一些语法错误。 a.seqreq 后缺少逗号 (,)。在第二个 case 语句中，它将是 case upper(a.via) when 'O' then a.online_date 而不是 case when upper(a.via) when 'O' then a.online_date。

SELECT a.seqreq,
b.idfieldb ,
c.idfieldc ,
a.number_given,
case upper(a.via) 
when 'O' then 'Online'
when 'M' then 'Manual'
else a.via
end as via,
case  upper(a.via) when 'O' then a.online_date
when 'M' then a.manual_date 
else a.others_date
end as date_registered
from mytablea a 
left join tbl_b b on a.idfielda=b.idfieldb
left join tbl_c c on a.idfielda=c.idfieldc
left join tbl_d d on a.userEntry=d.NoIdUser