SELECT * FROM TABLE
WHERE YEAR(date_created) = YEAR(CURRENT_DATE - INTERVAL 1 MONTH)
AND MONTH(date_created) = MONTH(CURRENT_DATE - INTERVAL 1 MONTH)

SELECT 
    DATEDIFF(CURRENT_DATE, t.geb_datum)/365 DIV 1 AS AlterInJahren,
FROM tabelle t 
LIMIT 100;