Question

I have a bunch of timestamped rows (using the ‘datetime’ data type)

I want to select all the rows that have a timestamp that is within a particular month.

The column is indexed so I can’t do MONTH(timestamp) = 3 because that’ll make this index unuseable.

If I have year and month variables (in perl), is there a horrific bit of SQL I can use like:

timestamp BETWEEN DATE($year, $month, 0) AND DATE($year, $month, 31);

But nicer, and actually works?

Answer 1

I would actually go with the idea you proposed ; maybe with a small difference :

select *
from your_table 
where date_field >= '2010-01-01'
    and date_field < '2010-02-01'

(Of course, up to you the use $year and $month properly)

Note the < '2010-02-01' part : you might have to consider this, if you have dates that include the time.

For instance, if you have a line with a date like '2010-01-31 12:53:12', you probably want to have that line selected — and, by default, '2010-01-31' means '2010-01-31 00:00:00'.

Maybe that doesn’t look ‘nice’ to the eye ; but it’ll work ; and use the index… It’s the kind of solution I generaly use when I have that kind of problem.