How do I get the first day of the week of a date in mysql?

Question

Suppose I have 2011-01-03 and I want to get the first of the week, which is sunday, which is 2011-01-02, how do I go about doing that?

The reason is I have this query:

select 
  YEAR(date_entered) as year, 
  date(date_entered) as week,   <-------This is what I want to change to select the first day of the week.
  SUM(1) as total_ncrs, 
  SUM(case when orgin = picked_up_at then 1 else 0 end) as ncrs_caught_at_station 
from sugarcrm2.ncr_ncr 
where 
sugarcrm2.ncr_ncr.date_entered > date('2011-01-01') 
and orgin in( 
'Silkscreen', 
'Brake', 
'Assembly', 
'Welding', 
'Machining', 
'2000W Laser', 
'Paint Booth 1', 
'Paint Prep', 
'Packaging', 
'PEM', 
'Deburr', 
'Laser ', 
'Paint Booth 2', 
'Toolpath' 
) 
and date_entered is not null 
and orgin is not null 
AND(grading = 'Minor' or grading = 'Major') 
 and week(date_entered) > week(current_timestamp) -20 
group by year, week(date_entered) 
order by year   asc, week asc 

And yes, I realize that origin is spelled wrong but it was here before I was so I can't correct it as too many internal apps reference it.

So, I am grouping by weeks but I want this to populate my chart, so I can't have all the beginning of weeks looking like different dates. How do I fix this?

Answer 1

If the week starts on Sunday do this:

DATE_ADD(mydate, INTERVAL(1-DAYOFWEEK(mydate)) DAY)

If the week starts on Monday do this:

DATE_ADD(mydate, INTERVAL(-WEEKDAY(mydate)) DAY);

more info