Find day values in bigint date? This query is working good.

select  DATENAME(DW,getdate()) AS [Weekday]


My Problem is suppose I give input values like

select  DATENAME(DW,InvoiceDate) AS [Weekday] from store;


is not working in SQL-Server 2008 R2.

Column datatype is BIGINT, column values below

InvoiceDate

20130925
20130926
20130927
20130928
20130929
20130930
Firstly, why on earth are you storing dates as BIGINT?! 

Date fields should be stored as dates, otherwise you could end up inserting invalid dates and you'll have trouble doing basic date calculations, as per now.

To answer your question, you'll need to CAST the InvoiceDate field, firstly to a VARCHAR, then to a DATE type:

SELECT DATENAME(WEEKDAY, CAST(CAST(InvoiceDate AS VARCHAR(10)) AS DATE)) AS [WeekDay]
    FROM Store;