根据列是否为null显示不同的显示值

Question

在这个查询中，我希望能够具有-对于attached_document列，如果有空值，我希望它输出"无附件"，否则对于那里的任何值，它都将是"有附件"。

select ev.actual_date, ev.event_name, ev.generic_description, ev.full_name as client_name, 
ev.staff_desc as staff, ev.user_entered_desc as entered_by, ev.attached_document
from event_view ev where event_name in
('Treatment Plan', 'Treatment Plan Rev.2', 'Treatment Plan Review',
'Treatment Plan Review Rev.2') and is_service_event = '1' 
order by event_name, actual_date, client_name

Answer 1

尝试

SELECT
ev.actual_date
,ev.event_name
,ev.generic_description
,ev.full_name         AS client_name
,ev.staff_desc        AS staff
,ev.user_entered_desc AS entered_by
,COALESCE(ev.attached_document,'No attachment') AS  attached_document
FROM
event_view ev
WHERE
event_name IN
(
'Treatment Plan'
,'Treatment Plan Rev.2'
,'Treatment Plan Review'
,'Treatment Plan Review Rev.2'
)
AND is_service_event = '1'
ORDER BY
event_name
,actual_date
,client_name;