Hi, you didn't join the
ApproveType
Table in your query.
SELECT DocumentInfo.DocID,
dbo.DocumentInfo.DocName,
dbo.DocumentInfo.Uploadfile,
dbo.DocType.DocType,
dbo.Department.DepType ,
dbo.ApproveType.ApproveType AS ApproveID
FROM dbo.DocumentInfo
LEFT JOIN dbo.DocType ON dbo.DocumentInfo.DocTypeID=dbo.DocType.DocTypeID
LEFT JOIN dbo.Department ON dbo.DocumentInfo.DepID=dbo.Department.DepID
You must join it in order to see the ApproveType column.
Hope it helps! :)