Question

I have all my data stamped with a field- dated which is in the format Y-m-d H:i- i would like to cast this field using mysql to represent the hour of the day so- 2011-11-21 15:28:05 would become 15- i have been reading the docs but it doesnt state whether or not you can specify a format

is this possible?

The idea is, I can count how many rows are stamped for each hour then display this in a graph.

this has been my working so far

SELECT CAST(dated AS TIME) FROM `posts` WHERE CAST(dated AS DATE) = CAST('".$start_date."' as DATE) AND type = '' ORDER by dated ASC;

Answer 1

Use date_format:

SELECT count(*), date_format(dated, "%Y:%m:%d %H") AS hour 
FROM posts 
GROUP BY hour

Or to get just the hour, regardless of day:

SELECT count(*), HOUR(dated) AS hour 
FROM posts 
GROUP BY hour