MYSQL 嘗試根據條件獲取值時出錯的情況

Question

為什么我收到此查詢錯誤？ 有什么我想念的嗎？

因此，如果“via”字段為 O，我想獲取 online_date，那么如果“via”字段為 MI，我想獲取 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

錯誤信息：

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

查詢中有一些語法錯誤。 在a.seqreq之后缺少逗號（，）。 在第二個case語句中，當 'O' 然后 a.online_date 時將是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