sql-server - 使用 UNION 时 SQL 返回的结果更少？

Question

我有一个 SQL Server 存储过程，当我添加联合和后半部分时，它没有给出所有结果。前半部分会给我所有 6 个结果，使用并集，我只得到 5 个。

有 3 位患者有自己的[图表编号]，每个患者都有 2 项应显示的项目。如果患者的两个条目的 [CPTCode] 相同，则当我添加并集时，仅显示两个条目之一(它为我提供了所有 6 个具有相同 [cptcode] 且没有并集的条目)。后半部分实际上并没有提取任何关于我现在正在做的事情的信息，但它是必要的。

select      /*Patients with chart numbers*/
   B1.[chart Number],
   '0' as newPatient, 
   isnull(Lytec.[Last Name],'') as [Last Name], 
   isnull(Lytec.[First Name],'') as [First Name],
   isnull(Address.[Name],
   Lytec.[Facility Code]) as [Facility], 
   isnull(B1.DOS,'') as [DOS], 
   isnull(Ins.[Name],
   Lytec.[Primary Code]) as [Primary Code],
   isnull(B1.[CPTCode],'') as cptCode, 
   isnull(B1.[Units],'') as [Units], 
   isnull(B1.[Modifiers],'') as [Modifiers], 
   isnull(B1.[cptCodeOther],'') as [cptCodeOther],
   isnull(B1.[cptCode2],'') as cptCode2, 
   isnull(B1.[Units],'') as [Units2], 
   isnull(B1.[Modifiers2],'') as [Modifiers2], 
   isnull(B1.[cptCodeOther2],'') as [cptCodeOther2],
   'name' as ProviderName
from 
   [sandboxmr].dbo.patient Lytec
   left join [dbo].[Billing] B1 on B1.[Chart Number] = Lytec.[Chart Number]
   left join [sandboxmr].dbo.[Address] Address on Lytec.[Facility Code] = Address.[Code]
   left join [sandboxmr].dbo.[Insurance] Ins on Lytec.[Primary Code] = Ins.[Code]
where 
   b1.[userid] = 54
   and (b1.[DateSubmitted] >= convert(varchar(25),'2011-8-31',101) 
   and b1.[DateSubmitted] <= convert(varchar(25),'2011-9-22',101))

union

select      /*Patients without chart numbers*/
   cast(P.id as varchar(15)) as [chart number], 
   '1' as newPatient,  
   isnull(P.[Last Name],'') as [Last Name], 
   isnull(P.[First Name],'') as [First Name],
   isnull(Address.[Name],
   P.[Facility Code]) as [Facility], 
   isnull(IV.DOS,isnull(SV.DOS,'')) as [DOS], 
   isnull(Ins.[Name],P.[Primary_Code]) as [Primary Code],
   isnull(IV.[cptCode],isnull(SV.[cptCode],'')) as cptCode, 
   isnull(IV.[Units],isnull(SV.[Units],'')) as [Units], 
   isnull(IV.[Modifiers],isnull(SV.[Modifiers],'')) as [Modifiers],    
   isnull(IV.[cptcodeother],isnull(SV.[cptcodeother],'')) as [cptCodeOther],
   isnull(IV.[cptCode2],isnull(SV.[cptCode2],'')) as cptCode2, 
   isnull(IV.Units2,isnull(SV.Units2,'')) as [Units2], 
   isnull(IV.[Modifiers2],isnull(SV.[Modifiers2],'')) as [Modifiers2], 
   isnull(IV.[cptCodeOther2],isnull(SV.[cptCodeOther2],'')) as [cptCodeOther2],
   'Name' as ProviderName
from 
   [DNSList].[dbo].[Patient] P 
   left join [dbo].[InitialVisits] IV on p.emr_id = IV.patientid
   left join [dbo].[SubsequentVisits] SV on p.emr_id = SV.patientid
   left join [sandboxmr].dbo.[Address] Address on P.[Facility Code] = Address.[Code]
left join [sandboxmr].dbo.[Insurance] Ins on P.[Primary_Code] = Ins.[Code]
where 
   p.[userid] = 54 
   and p.[Chart Number] is null
   and (p.[DateSubmitted] >= convert(varchar(25),'2011-8-31',101) 
   and p.[DateSubmitted] <= convert(varchar(25),'2011-9-22',101))
order by 
   [Last Name]

为什么会这样，我该如何解决？我尝试将 distinct 添加到 [cptcode] 区域，但它当然会生成错误。

感谢您提供的任何帮助!

Answer 1

UNION 将消除重复的行，无论它们是位于两个结果集之间，还是在您的情况下，仅位于一个结果集中。尝试使用 UNION ALL 代替。