SQL子选择返回多个值

Question

我想统计未来约会在同一天进行激活约会位置。我预计给定日期范围的每个Patient_ID有多个计数。我不确定是否需要临时表或子查询是否可用。

从下面这个代码是我的错误：

子查询返回多个值。当 子查询遵循=，！=，<，< =，>，> =或当子查询用作 表达式时，这是不允许的。

定义：

• Appointment_DateTime - （日期）是实际约会事件
• DateTime_Scheduled - （日期）是未来的约会
• 说明的记录标记 - （文字）是位置描述
• Patient_ID - （int）是唯一的患者ID
• Appointment_ID - （int）是唯一的约会ID

SQL

SELECT 
    loc.Description 
,Count(app.Appointment_ID) 

FROM [Ntier_HARH].[PM].[Appointments] app 

join [Ntier_HARH].[PM].[Resources] res 
    on res.Resource_ID = app.Resource_ID 
join [Ntier_HARH].[PM].[Practitioners] doc 
    on doc.Practitioner_ID = res.Practitioner_ID 
join [Ntier_HARH].[PM].[Scheduling_Locations] loc 
    on loc.Scheduling_Location_ID = app.Scheduling_Location_ID 

where  
    cast(app.DateTime_Scheduled as date) = '2017-01-16' 
    and app.status <> 'X' 
    and cast(app.Appointment_DateTime as date) = 
     (Select cast(DateTime_Scheduled as date) 
     from [Ntier_HARH].[PM].[Appointments] 
     where Patient_ID = app.Patient_ID) 

group by loc.Description 

Answer 1

您可以使用的in代替=

where 

cast(app.DateTime_Scheduled as date) = '2017-01-16' 
and app.status <> 'X' 
and cast(app.Appointment_DateTime as date) IN (Select cast(DateTime_Scheduled as date) from [Ntier_HARH].[PM].[Appointments] where Patient_ID = app.Patient_ID) 

group by loc.Description 

Answer 2

你不也是由PatientId需要组？如果您只想按位置进行约会计数，则子查询不是必需的。我不明白为什么其他两张桌子也是必需的。

SELECT l.Description, Count(a.Appointment_ID) 

FROM [Ntier_HARH].[PM].[Appointments] a 
    join [Ntier_HARH].[PM].[Scheduling_Locations] l 
     on l.Scheduling_Location_ID = a.Scheduling_Location_ID 

where cast(a.DateTime_Scheduled as date) = '2017-01-16' 
    and a.status <> 'X' 

group by l.Description