How to truncate a date to the beginning of week (Sunday)?

Question

I need to truncate dates to the start of week, which is Sunday in my case. How can I do this in PostgreSQL? This truncates to Monday:

date_trunc('week', mydate)

Answer 1

If you subtract the dow value (0 for Sundays, 6 for Saturdays) from the current date than you get the previous Sunday which is the begin of your Sunday-based week

demo:db<>fiddle

SELECT 
    my_date - date_part('dow', my_date)::int
FROM
    my_table

Further reading, documentation