case，cast

UPDATE dbo.Dat_Camera SET Cam_Config='<xml><cam><type>2</type>'
+CASE WHEN Cam_DX_VideoId is NOT NULL  THEN
  '<naming>'+CAST(Cam_DX_VideoId AS NVARCHAR(128))+'</naming>' END
+'</cam></xml>'  
 WHERE CamId=1020184

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原文地址：https://www.cnblogs.com/change4now/p/5665168.html