Multiple joins on same table? - sql

Question

I have two table:
tbl_EmploymentSegmentEM:
╔══════╦═════════════╦════════════╦═══════════════╦═══════════════════════════════╦════════════╦═════════════╦══════════════════════════╦════════════════╗
║ SrNo ║ CIBILTuefID ║ Prospectno ║ ApplicantType ║ ApplicantName ║ SegmentTag ║ AccountType ║ DateReportedandCertified ║ OccupationCode ║
╠══════╬═════════════╬════════════╬═══════════════╬═══════════════════════════════╬════════════╬═════════════╬══════════════════════════╬════════════════╣
║ 1 ║ 1 ║ 718580 ║ APPLICANT ║ RAJKUMAR GIRISHCHANDRA PANDEY ║ E01 ║ 10 ║ 31122014 ║ 02 ║
║ 2 ║ 4 ║ 718638 ║ APPLICANT ║ Anil Kumar Aggarwal ║ E01 ║ 10 ║ 31122014 ║ 01 ║
╚══════╩═════════════╩════════════╩═══════════════╩═══════════════════════════════╩════════════╩═════════════╩══════════════════════════╩════════════════╝
tbl_CIBILFieldDescription:
╔════════╦══════════╦══════════════════════════════╦═══════╦═════════════════════════════╗
║ Header ║ FieldTag ║ FieldName ║ Value ║ ValueDescription ║
╠════════╬══════════╬══════════════════════════════╬═══════╬═════════════════════════════╣
║ PT ║ 03 ║ TelephoneType ║ 03 ║ Office Phone ║
║ EM ║ 03 ║ OccupationCode ║ 01 ║ Salaried ║
║ EM ║ 03 ║ OccupationCode ║ 02 ║ Self Employed Professional. ║
║ EM ║ 03 ║ OccupationCode ║ 03 ║ Self Employed ║
║ EM ║ 03 ║ OccupationCode ║ 04 ║ Others ║
║ EM ║ 05 ║ NetGrossIncomeIndicator ║ G ║ Gross Income ║
║ EM ║ 05 ║ NetGrossIncomeIndicator ║ N ║ Net Income ║
║ EM ║ 06 ║ MonthlyAnnualIncomeIndicator ║ M ║ Net Monthly ║
║ EM ║ 06 ║ MonthlyAnnualIncomeIndicator ║ A ║ Net Annual ║
║ SC ║ 01 ║ ScoreCardName ║ 01 ║ CIBILTUSCR ║
╚════════╩══════════╩══════════════════════════════╩═══════╩═════════════════════════════╝
I am trying to get Account Type and Occupation code description from tbl_CIBILFieldDescription for the corresponding values.
I tried this :
SELECT DISTINCT CIBILTuefID,
Prospectno,
ApplicantType,
ApplicantName,
SegmentTag,
AccountType,
DateReportedandCertified,
OccupationCode,
mst.ValueDescription AS OccupationCodeDesc,
Income,
NetGrossIncomeIndicator,
mst.ValueDescription AS NetGrossIncomeIndicatorDesc,
MonthlyAnnualIncomeIndicator,
DateofEntryforErrorCode,
ErrorCode,
DateofEntryforCIBILRemarksCode,
CIBILRemarksCode,
DateofEntryforErrorDisputeRemarksCode,
ErrorDisputeRemarksCode1,
ErrorDisputeRemarksCode2,
MkrId,
MkdDt
FROM tbl_EmploymentSegmentEM EM
INNER JOIN tbl_CIBILFieldDescription mst
ON 1 = 1
WHERE mst.Header = 'EM'
AND mst.FieldName = 'OccupationCode'
AND mst.Value = EM.OccupationCode
And it seems to work ok for OccupationCode but what if I want both OccupationCode and AccountType from the same query? What is the best way to do this?

Answer 1

You can join your table multiple times using LEFT JOIN:
SELECT DISTINCT cibiltuefid,
prospectno,
applicanttype,
applicantname,
segmenttag,
accounttype,
datereportedandcertified,
occupationcode,
mst.valuedescription AS OccupationCodeDesc,
income,
netgrossincomeindicator,
mst1.valuedescription AS NetGrossIncomeIndicatorDesc,
monthlyannualincomeindicator,
dateofentryforerrorcode,
errorcode,
dateofentryforcibilremarkscode,
cibilremarkscode,
dateofentryforerrordisputeremarkscode,
errordisputeremarkscode1,
errordisputeremarkscode2,
mkrid,
mkddt
,mst.ValueDescription AS Occupation
,mst1.ValueDescription AS Account
FROM tbl_employmentsegmentem EM
LEFT JOIN tbl_cibilfielddescription mst
ON mst.fieldname = 'OccupationCode'
AND mst.value = EM.occupationcode
AND mst.header = 'EM'
LEFT JOIN tbl_cibilfielddescription mst1
ON mst1.fieldname = 'AccountType'
AND mst1.value = EM.accounttype
AND mst1.header = 'EM'