It looks like you have some non numeric data in your column. Maybe this would help:select

*

from

thangela.NpowerNorthern_v1 a

INNER JOIN

(

SELECT

--Columns needed,

CAST( b.MPANCORE AS numeric(17,2) AS MPANCORE

FROM

EPPS.dbo.Customers b

WHERE

b.MPANCORE NOT LIKE '%[^0-9.-]%'

) AS T

ON T.MPANCORE = a.MPAN1 EDIT - I didn't read your post correctly. I though you were doing a calculation. So I changed the code.