SELECT ROUND((DATEDIFF(max(atendido_em_data),min(atendido_em_data)))/7) as semana,min(atendido_em_data) as min,max(atendido_em_data) as max
from ger_posicao;

SELECT DAYNAME(data),
       data,
       CONCAT('semana ', WEEK(data,1) - WEEK('20180428',1) + 1) AS semana
FROM tabela