將非標準連接轉換爲標準連接

Question

我試圖重做一個查詢，以便它使用標準連接（在from子句中）而不是舊版本（遷移到SQL服務器以便強制執行此轉換）。我遇到的問題是我下面的查詢版本返回的記錄比原始記錄少得多。所以我認爲我的一個外連接不是那麼外在。感謝您的幫助，特別是如果您真的通過整個查詢。我似乎無法找到任何有關如何進行這種轉換的良好文檔。

declare 
@startdate datetime, @enddate datetime 

select @startdate = dateadd(dd,-6,convert(datetime,convert(varchar,getdate(),101))) 
select @enddate = dateadd(dd,6,@startdate) 

SELECT PAT.CUSID as ID , 
     substring(CPTREC.CompletedDateTime,1,12) AS DateOfService, 
     SUBSTRING(PCMH.ProcedureCode,CHARINDEX('-',PCMH.ProcedureCode)+ 1,50) AS CPT_Code 
FROM cpt_records as CPTREC 
left Outer Join ProcedureCodeMH as PCMH 
    on CPTREC.ProcedureCodeRevCount = PCMH.ProcedureCodeRevCount 
     and CPTREC.ProcedureCodeSer= PCMH.ProcedureCodeSer 
left outer join Credit as CR 
    on CPTREC.ActInstProcCodeSer = CR.ActInstProcCodeSer 
     and CPTREC.ActInstProcCodeRevCount = CR.ActInstProcCodeRevCount 
inner join ActivityInstance as ACTIN 
    on CPTREC.ActivityInstanceSer= ACTIN.ActivityInstanceSer 
     and CPTREC.ActivityInstanceRevCount = ACTIN.ActivityInstanceRevCount 
inner join ActivityCapture as ACTCAP 
    on ACTCAP.ActivityInstanceSer= ACTIN.ActivityInstanceSer 
     and ACTCAP.ActivityInstanceRevCount = ACTIN.ActivityInstanceRevCount 
inner join ActCaptDiagnosisMH as ACTCAPDMH 
    on ACTCAPDMH.ActivityCaptureSer = ACTCAP.ActivityCaptureSer 
     and ACTCAPDMH.ActivityCaptureRevCount=ACTCAP.ActivityCaptureRevCount 
left outer join Department as DEPT 
    on ACTCAP.DepartmentSer = DEPT.DepartmentSer 
left outer join Hospitality as HOSP 
    on DEPT.HospitalitySer = HOSP.HospitalitySer 
Left outer join Diagnosis as DIAG 
    on ACTCAPDMH.DiagnosisSer = DIAG.DiagnosisSer 
inner join TemplateCycle as TEMPCYC 
    on ACTIN.TemplateCycleSer= TEMPCYC.TemplateCycleSer 
inner join Template as PLATE 
    on TEMPCYC.TemplateSer = PLATE.TemplateSer 
inner join Patent as PAT 
    on PLATE.PatentSer = PAT.PatentSer 
Left Outer Join PatentParticular as PATPAR 
    on PAT.PatentSer = PATPAR.PatentSer 
inner join PatentDoctor as PATDOC 
    on PAT.PatentSer = PATDOC.PatentSer 
inner join Doctor as DOC 
    on PATDOC.ResourceSer = DOC.ResourceSer 
WHERE (CPTREC.CompletedDateTime >= @startdate) 
    and (CPTREC.CompletedDateTime < dateadd(dd,1,@enddate)) 
    and (CPTREC.ObjectStatus = 'Active') 
    and (PATDOC.OncologistFlag = 0) 
    and (PATDOC.PrimaryFlag = 1) 
    and (PCMH.ProcedureCode like '%77781%' 
      or PCMH.ProcedureCode like '%77782%' 
      or PCMH.ProcedureCode like '%77783%' 
      or PCMH.ProcedureCode like '%77784%' 
      or PCMH.ProcedureCode like '%77785%' 
      or PCMH.ProcedureCode like '%77786%' 
      or PCMH.ProcedureCode like '%77787%') 

---

是帶回更多的記錄的原始是

---

SELECT PAT.CUSID as ID , substring(cpt_records.CompletedDateTime,1,12) AS DateOfService, SUBSTRING(ProcedureCodeMH.ProcedureCode,CHARINDEX('-',ProcedureCodeMH.ProcedureCode)+ 1,50) AS CPT_Code INTO cpt777 FROM cpt_records , ActivityCapture , ActivityInstance , Patent as PAT, ProcedureCodeMH , Template , TemplateCycle , Department , Hospitalityity , Credit , Doctor, PatentDoctor , ActCaptDiagnosisMH , Diagnosis , PatentParticular WHERE (#cpt_records.ProcedureCodeSer *= ProcedureCodeMH.ProcedureCodeSer) and 

(ProcedureCodeMH.ProcedureCodeRevCount =*cpt_records.ProcedureCodeRevCount) and 

(ActivityCapture.DepartmentSer *= Department.DepartmentSer) and 

(Department.HospitalitySer *= Hospitality.HospitalitySer) and 

(ActivityCapture.ActivityCaptureSer *= Credit.ActivityCaptureSer) and 

(ActivityCapture.ActivityCaptureRevCount *= Credit.ActivityCaptureRevCount) and 

(Credit.ActInstProcCodeSer =* cpt_records.ActInstProcCodeSer) and 

(Credit.ActInstProcCodeRevCount =* cpt_records.ActInstProcCodeRevCount) and 

(Patent.PatentSer *= PatentParticular.PatentSer) and 

(cpt_records.ActivityInstanceSer = ActivityInstance.ActivityInstanceSer) and 

(cpt_records.ActivityInstanceRevCount = ActivityInstance.ActivityInstanceRevCount) and 

(ActivityInstance.ActivityInstanceSer = ActivityCapture.ActivityInstanceSer) and 

(ActivityInstance.ActivityInstanceRevCount = ActivityCapture.ActivityInstanceRevCount) and 

(Patent.PatentSer = Template.PatentSer) and 

(Template.TemplateSer = TemplateCycle.TemplateSer) and 

(TemplateCycle.TemplateCycleSer = ActivityInstance.TemplateCycleSer) and 

(Patent.PatentSer = PatentDoctor.PatentSer) and 

(PatentDoctor.ResourceSer = Doctor.ResourceSer) and 

(ActivityCapture.ActivityCaptureSer = ActCaptDiagnosisMH.ActivityCaptureSer) and 

(ActivityCapture.ActivityCaptureRevCount = ActCaptDiagnosisMH.ActivityCaptureRevCount) and (cpt_records.CompletedDateTime >= @startdate) and 

(cpt_records.CompletedDateTime < dateadd(dd,1,@enddate)) and 

(cpt_records.ObjectStatus = 'Active') and 

(PatentDoctor.OncologistFlag = 0) and 

(PatentDoctor.PrimaryFlag = 1) and 

(ActCaptDiagnosisMH.DiagnosisSer *= Diagnosis.DiagnosisSer) and 

(ProcedureCodeMH.ProcedureCode like '%77781%' or ProcedureCodeMH.ProcedureCode like '%77782%' or ProcedureCodeMH.ProcedureCode like '%77783%' or ProcedureCodeMH.ProcedureCode like '%77784%' or ProcedureCodeMH.ProcedureCode like '%77785%' or ProcedureCodeMH.ProcedureCode like '%77786%' or ProcedureCodeMH.ProcedureCode like '%77787%') 

Answer 1

的問題是左連接爲在沒有找到匹配的行的聯接的列值，則返回空值，但您正在檢查where子句中的那些列值，但where謂詞是在執行後所有行ar e加入，所以他們永遠不會匹配，你的外部連接被擊沉。

即本例中查詢：

select * 
from table1 t1 
left join table2 t2 on t2.fk = t1.id 
where t2.col1 = 'x' 

將永遠返回不具備相應table2行任何行，因爲col1將null，並與null比較始終false，除了col1 is null。

要解決這個問題，就需要測試移動到ON條款，因此比較發生而join正在取得，像這樣：

select * 
from table1 t1 
left join table2 t2 on t2.fk = t1.id and t2.col1 = 'x' 

現在左連接仍然會返回行同時在關鍵字上進行匹配，並應用額外的謂詞來進一步優化匹配。

在你的情況，你正在做外（即left）加入到ProcedureCodeMH as PCMH，但WHERE條款，類似於上面的第一個例子中的測試PCMH列。

你的查詢重寫將被（見這裏的變化是行註釋）：

SELECT PAT.CUSID as ID , 
     substring(CPTREC.CompletedDateTime,1,12) AS DateOfService, 
     SUBSTRING(PCMH.ProcedureCode,CHARINDEX('-',PCMH.ProcedureCode)+ 1,50) AS CPT_Code 
FROM cpt_records as CPTREC 
left Outer Join ProcedureCodeMH as PCMH 
    on CPTREC.ProcedureCodeRevCount = PCMH.ProcedureCodeRevCount 
     and CPTREC.ProcedureCodeSer= PCMH.ProcedureCodeSer 
     -- MOVED THIS TEST FROM WHERE CLAUSE TO HERE 
     and (PCMH.ProcedureCode like '%77781%' 
       or PCMH.ProcedureCode like '%77782%' 
       or PCMH.ProcedureCode like '%77783%' 
       or PCMH.ProcedureCode like '%77784%' 
       or PCMH.ProcedureCode like '%77785%' 
       or PCMH.ProcedureCode like '%77786%' 
      or PCMH.ProcedureCode like '%77787%') 
left outer join Credit as CR 
    on CPTREC.ActInstProcCodeSer = CR.ActInstProcCodeSer 
     and CPTREC.ActInstProcCodeRevCount = CR.ActInstProcCodeRevCount 
inner join ActivityInstance as ACTIN 
    on CPTREC.ActivityInstanceSer= ACTIN.ActivityInstanceSer 
     and CPTREC.ActivityInstanceRevCount = ACTIN.ActivityInstanceRevCount 
inner join ActivityCapture as ACTCAP 
    on ACTCAP.ActivityInstanceSer= ACTIN.ActivityInstanceSer 
     and ACTCAP.ActivityInstanceRevCount = ACTIN.ActivityInstanceRevCount 
inner join ActCaptDiagnosisMH as ACTCAPDMH 
    on ACTCAPDMH.ActivityCaptureSer = ACTCAP.ActivityCaptureSer 
     and ACTCAPDMH.ActivityCaptureRevCount=ACTCAP.ActivityCaptureRevCount 
left outer join Department as DEPT 
    on ACTCAP.DepartmentSer = DEPT.DepartmentSer 
left outer join Hospitality as HOSP 
    on DEPT.HospitalitySer = HOSP.HospitalitySer 
Left outer join Diagnosis as DIAG 
    on ACTCAPDMH.DiagnosisSer = DIAG.DiagnosisSer 
inner join TemplateCycle as TEMPCYC 
    on ACTIN.TemplateCycleSer= TEMPCYC.TemplateCycleSer 
inner join Template as PLATE 
    on TEMPCYC.TemplateSer = PLATE.TemplateSer 
inner join Patent as PAT 
    on PLATE.PatentSer = PAT.PatentSer 
Left Outer Join PatentParticular as PATPAR 
    on PAT.PatentSer = PATPAR.PatentSer 
inner join PatentDoctor as PATDOC 
    on PAT.PatentSer = PATDOC.PatentSer 
inner join Doctor as DOC 
    on PATDOC.ResourceSer = DOC.ResourceSer 
WHERE CPTREC.CompletedDateTime >= @startdate 
and CPTREC.CompletedDateTime < dateadd(dd,1,@enddate) 
and CPTREC.ObjectStatus = 'Active' 
and PATDOC.OncologistFlag = 0 
and PATDOC.PrimaryFlag = 1 

注：inner join可以簡化爲簡單join - inner是默認的連接類型。