我正在尝试从约会数据库返回一份报告。我附上了我当前的 sql 查询，我遇到的困难是当我“加入”我的客户联系人表时，即
join contacts on (customer.entity_id = contact.contact_id and contacts.arch = 'contact.phonenumber')
join contact_detail on (contact_detail.contact_id = contacts.contact_id and contact_detail.lookup = 'mobile')
我会立即失去在该表和详细信息表上没有条目的所有客户，我希望实现的是，如果客户没有联系人条目，它会为这些字段返回空值。即在我添加加入之前它可能已经消失了
Name Time note Mobile
DAVID 8pm haircut 0412656865
Julie 8pm style
Daniel 8pm Colour 0412533535
但是添加了这些行
DAVID 8pm haircut 0412656865
Daniel 8pm Colour 0412533535
它不包括朱莉，因为她没有联系电话号码
这就是简单的问题。我希望朱莉返回 NULL 值
该系统使用带有 java 原型驱动前端的 mysql 数据库，因此我们使用实体表、行为表、参与，然后是一些详细信息和查找表。
实际的sql查询是
select
p.activity_start_time
, p.activity_end_time
, p.activity_start_time AS start_time
, p.activity_end_time as end_time
, a.status
, a.description AS appointmentnote
, e.name as patientname
, e.description AS patientdescription
, customer.name as customername
, customer.description as customerdescription
, sd.name as schedule_name
, eAt.name as appointment_type
, mobile.description as Mobile
from acts a
join participations p on
a.act_id=p.act_id and a.arch_short_name='act.customerAppointment' and
p.act_arch_short_name='act.customerAppointment'
join entities e on p.entity_id=e.entity_id
join participations pAt on a.act_id=pAt.act_id and
a.arch_short_name='act.customerAppointment' and
pAt.arch_short_name='participation.appointmentType'
join entities eAt on pAt.entity_id=eAt.entity_id
left join entity_relationships er ON (er.target_id = e.entity_id
AND er.active_start_time <= date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND)
AND ((er.active_end_time >= date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND)) OR (er.active_end_time IS NULL)))
left join entities customer ON
(customer.entity_id = er.source_id AND customer.arch_short_name = 'party.customerperson')
join contacts mobile on (mobile.party_id = customer.entity_id AND mobile.arch_short_name = 'contact.phoneNumber')
join contact_classifications mb_class on (mb_class.contact_id = mobile.contact_id AND mb_class.lookup_id = '120')
join participations schedule on
a.act_id=schedule.act_id and schedule.arch_short_name='participation.schedule'
left join entities sd on
(sd.entity_id = schedule.entity_id)
left outer join act_details d on
a.act_id=d.act_id
where (p.activity_start_time<date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND)
and p.activity_end_time>date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND) or
p.activity_start_time<date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND)
and p.activity_end_time>date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND) or
p.activity_start_time>=date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND) and
p.activity_end_time<=date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND)) and
(schedule.activity_start_time<date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND) and
schedule.activity_end_time>date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND) or
schedule.activity_start_time<date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND) and
schedule.activity_end_time>date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND) or
schedule.activity_start_time>=date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "00:00:00" HOUR_SECOND) and
schedule.activity_end_time<=date_add((date_format('2013-07-24',"%Y-%m-%d")),
INTERVAL "23:59:59" HOUR_SECOND)) and
e.arch_short_name = 'party.patientpet' and
customer.arch_short_name = 'party.customerperson'
and sd.name like CONCAT('GROOM','%')
order by p.activity_start_time, sd.name, a.act_id