Bhuvnesh,

CROSS APPLY (

VALUES(High, 'High', DATEPART(dw, CAST(DateID AS CHAR(8))))

,(Low, 'Low', DATEPART(dw, CAST(DateID AS CHAR(8))))) a (Val, Type, weekday)

GROUP BY CompanyName, Type

is similar to

CROSS APPLY (

select High as val , 'High' as Type , DATEPART(dw, CAST(DateID AS CHAR(8))) as Weekday

union all

select Low as val, 'Low' as Type , DATEPART(dw, CAST(DateID AS CHAR(8)))

) a

GROUP BY CompanyName, Type

Hope you understood..

Thanks,

Saurabh