求解：怎么通过判断，在视图中获取不同的列值_Sql Server

求解：如何通过判断，在视图中获取不同的列值
建了一个por_inv的视图：
SELECT dbo.invdtf.fitemno, dbo.invdtf.fwhcd, dbo.invdtf.flotno2, dbo.invdtf.flotno,
dbo.invdtf.fcoilno1, dbo.invdtf.fvendinvc, dbo.porecf_porlsf.mfcoilno1,
dbo.porecf_porlsf.fitemno AS fitemno_b
FROM dbo.invdtf RIGHT OUTER JOIN
dbo.porecf_porlsf ON dbo.invdtf.fcoilno1 = dbo.porecf_porlsf.mfcoilno1

现在想通过判断表invdtf中fvendinvc的值是否是"以S开头并且len(fvendinvc)= 18"来取值
如果是，则取视图中的fitemno，如果不是，在取fitemno_b

------解决方案--------------------

SQL code

SELECT CASE WHEN fvendinvc LIKE 'S%' AND len(fvendinvc)= 18 THEN fitemno ELSE fitemno_b END AS fitemnoFROM por_inv
------解决方案--------------------
SQL codeselect (case when left(dbo.invdtf.fvendinvc,1)='S' then dbo.invdtf.fitemno else dbo.porecf_porlsf.fitemno end) AS fitemno,  dbo.invdtf.fwhcd, dbo.invdtf.flotno2, dbo.invdtf.flotno,    dbo.invdtf.fcoilno1, dbo.invdtf.fvendinvc, dbo.porecf_porlsf.mfcoilno1FROM dbo.invdtf RIGHT OUTER JOIN  dbo.porecf_porlsf ON dbo.invdtf.fcoilno1 = dbo.porecf_porlsf.mfcoilno1
------解决方案--------------------
SQL codeCASE WHEN fvendinvc LIKE 'S%' AND len(fvendinvc)= 18 THEN fitemno ELSE fitemno_b END AS fitemno