Sql 同一个表上有多个联接？

我有两张桌子：

tbl\U就业细分市场项目：

╔══════╦═════════════╦════════════╦═══════════════╦═══════════════════════════════╦════════════╦═════════════╦══════════════════════════╦════════════════╗
║ 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 ║
╚══════╩═════════════╩════════════╩═══════════════╩═══════════════════════════════╩════════════╩═════════════╩══════════════════════════╩════════════════╝

╔════════╦══════════╦══════════════════════════════╦═══════╦═════════════════════════════╗
║ 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                  ║
╚════════╩══════════╩══════════════════════════════╩═══════╩═════════════════════════════╝

tbl\u CIBILFieldDescription:

╔══════╦═════════════╦════════════╦═══════════════╦═══════════════════════════════╦════════════╦═════════════╦══════════════════════════╦════════════════╗
║ 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 ║
╚══════╩═════════════╩════════════╩═══════════════╩═══════════════════════════════╩════════════╩═════════════╩══════════════════════════╩════════════════╝

╔════════╦══════════╦══════════════════════════════╦═══════╦═════════════════════════════╗
║ 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                  ║
╚════════╩══════════╩══════════════════════════════╩═══════╩═════════════════════════════╝

我正在尝试从

tbl\u CIBILFieldDescription

获取相应值的帐户类型和职业代码说明

我试过这个：

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 

---

对于

职业代码

来说，它似乎还可以，但是如果我希望从同一个查询中同时使用

职业代码

和

帐户类型

，该怎么办？最好的方法是什么

您可以使用

LEFT join

多次加入表：

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'

---

内部连接。。。。ON 1=1

请解释此联接试图实现的功能。这是交叉联接，即类似于具有WHERE子句中指定的联接条件的旧式联接……除了左联接而不是内部联接之外，我正在做完全相同的事情。谢谢，威尔马克回答。