SELECT a.WebIncrementID as order_ID,b.Quantity,b.[Shipment Date],
CASE when a.No_ = b.[Document No_] THEN 'Shipdata' ELSE 'shipdata' END flag  FROM [Tile Mountain$Sales Invoice Header] a
INNER JOIN [Tile Mountain$Sales Invoice Line] b on(a.No_ = b.[Document No_])

UNION ALL

SELECT a.WebIncrementID as order_ID,c.Quantity,c.[Shipment Date],
CASEwhen a.No_ = c.[Document No_] THEN 'nonShipdata' ELSE 'nonshipdata' END flag  FROM [Tile Mountain$Sales Header] a
INNER JOIN [Tile Mountain$Sales Line] c on(a.No_ = c.[Document No_])