SELECT COUNT(1)
FROM FB
WHERE
Dte BETWEEN CAST(YEAR(GETDATE()) AS VARCHAR(4)) + '-' + CAST(MONTH(DATEADD(month, -1, GETDATE())) AS VARCHAR(2)) + '-20 00:00:00'
AND CAST(YEAR(GETDATE()) AS VARCHAR(4)) + '-' + CAST(MONTH(GETDATE()) AS VARCHAR(2)) + '-20 00:00:00'