Thanks all I ended up using:
SELECT
tblDealsTeamreport.[CIBR Deal ID],
tblSalesTeamreport.[Team Member Name],
tblDealsTeamreport.[Associate Name],
IIf(IsNull(tblNamesCIBRtoSF.[SF Name]),tblDealsTeamreport.[Associate Name],tblNamesCIBRtoSF.[SF Name]) AS [New Associate Name]...