看了下你SQL没啥问题，你这是navicat 显示问题吧，你把最后一个字段的宽度拉宽一点，看你应该是显示不全

你小数位保留的太多了，可以用round()留两位小数

参考这个

https://www.jb51.net/database/2854728wq.htm

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SELECT D.日期,       

       D.金额 AS 金额,

       C.SUPPLIER_NAME AS 供应商,       

       LAG(D.金额) OVER(PARTITION BY C.SUPPLIER_NAME ORDER BY D.日期) AS 上期金额

  FROM (        

        SELECT CONVERT(VARCHAR(7), A.DOC_DATE, 23) as 日期,

                SUM(B.AMT_FC) AS 金额,

                SETTLEMENT_SUPPLIER_ID

          FROM PAYABLE_DOC A        

          LEFT JOIN PAYABLE_DOC_D B        

            ON A.PAYABLE_DOC_ID = B.PAYABLE_DOC_ID        

         where A.DOC_DATE >= DATEADD(year, -2, GETDATE())        

         GROUP BY CONVERT(VARCHAR(7), A.DOC_DATE, 23), SETTLEMENT_SUPPLIER_ID) AS D

  left join SUPPLIER C

    ON D.SETTLEMENT_SUPPLIER_ID = C.SUPPLIER_BUSINESS_ID

 WHERE

 C.SUPPLIER_NAME like '%肯纳司太%'

 GROUP BY D.日期, C.SUPPLIER_NAME

这样是可以的

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SELECT 

tmp.日期,

tmp.供应商,

tmp.金额 as 当期金额,

LAG(tmp.金额, 1) OVER (PARTITION BY tmp.供应商 ORDER BY tmp.日期) AS 环比金额

 FROM

(

SELECT 

CONVERT(VARCHAR(7),A.DOC_DATE,23) as 日期,

SUM(B.AMT_FC) AS 金额,

C.SUPPLIER_NAME AS 供应商

FROM PAYABLE_DOC A 

LEFT JOIN PAYABLE_DOC_D B ON A.PAYABLE_DOC_ID=B.PAYABLE_DOC_ID

left join SUPPLIER b on SETTLEMENT_SUPPLIER_ID=C.SUPPLIER_BUSINESS_ID

where A.DOC_DATE>=DATEADD(year,-2,GETDATE())

and   C.SUPPLIER_NAME like '%肯纳司太%'

GROUP BY CONVERT(VARCHAR(7),A.DOC_DATE,23),C.SUPPLIER_NAME

) tmp

我电脑中测试的环比查询，按年月与供应商分开了的