começar a segunda-feira da semana atual sql
SELECT CURDATE() - INTERVAL WEEKDAY(CURDATE()) DAY AS startweek;
obter o dia da semana a partir da data em sql
SELECT TO_CHAR(your_table.date_colunm, 'DAY')
FROM your_table;
o sql server obter datas da semana de número da semana
SELECT
DATEADD(DAY, 2 - DATEPART(WEEKDAY, GETDATE()), CAST(GETDATE() AS DATE)) [Week_Start_Date],
DATEADD(DAY, 8 - DATEPART(WEEKDAY, GETDATE()), CAST(GETDATE() AS DATE)) [Week_End_Date]