Question

I have a table like so:

id | gallons_used | date
----------------------
1    2             157263300
2    5             157262000
...

I want to get a result set containing only records that took place on X day of the week (Monday or Tuesday or Wednesday, etc etc)

Answer 1

Use DAYNAME() in your WHERE clause

WHERE DAYNAME(FROM_UNIXTIME(`date`)) = 'Monday'  <-- by day of the week
  AND `date` < INTERVAL CURRENT_DATE - 7 DAY     <-- within the last week

You can use DAYOFWEEK() as well but this is more readable.