Question

I have a MySQL database with the following columns:

id (INT)
duration (FLOAT)
start_date (DATETIME)

I would like to get modal statistics (frequency counts) for the duration and start_date columns.

Sorting the duration of an event by frequency was straightforward:

SELECT duration, COUNT(duration) 
AS frequency 
FROM trips 
GROUP BY duration 
ORDER BY frequency 
DESC;

If I run this same query on the start_date column, I get results of the form:

(datetime.datetime(2012, 8, 20, 15, 22), 6L)

(I’m using python to access the database). However, receiving my queries binned by the minute isn’t necessarily helpful — month, day of the week and hour are much more useful queries. I’ve tried changing the query to:

SELECT MONTH(start_date), COUNT(MONTH(start_date)) 
AS frequency 
FROM trips 
GROUP BY start_date 
ORDER BY frequency 
DESC;

However, if I do this then I start getting errors about my SQL syntax (Error 1064). I haven’t been able to figure out what the error is, unfortunately.

I’ve considered putting the year, month, day of the week, hour, minute, etc. in different columns, but I feel that it should be possible to select the subfield of the datetime field within a query.

thanks!

Answer 1

Count frequency of start_date months:

SELECT YEAR(start_date), MONTH(start_date), COUNT(*) AS frequency
FROM trips
GROUP BY YEAR(start_date), MONTH(start_date)
ORDER BY frequency DESC;

Count frequency of durations:

SELECT duration, COUNT(*) AS frequency
FROM trips
GROUP BY duration
ORDER BY frequency DESC;