DECLARE @tbl TABLE

(

ID INT IDENTITY(1,1),

SomeData VARCHAR(100)

)

INSERT INTO @tbl SELECT 'NA11345'

INSERT INTO @tbl SELECT 'NA113456'

INSERT INTO @tbl SELECT 'RA11345'

UPDATE @tbl SET SomeData = SUBSTRING(SomeData,CHARINDEX('NA',SomeData)+2,LEN(SomeData))

WHERE CHARINDEX('NA',SomeData) = 1

select * from @tbl