MySQL GROUP BY and Fill Empty Rows

Question

I\'m sure this has been answered before, but I can\'t find it in the detail that I need.

For an analytics system I need to be able to group rows and return them on a

Answer 1

In this answer I will outline how to generate your calendar tables.

Create three tables for days, hours and minutes:

CREATE TABLE days (
  day DATE,
  PRIMARY KEY (day)
) 
CREATE TABLE hours (
  hour INT,
  PRIMARY KEY (hour)
) 
CREATE TABLE minutes (
  minute INT,
  PRIMARY KEY (minute)
) 

Fill the hours table with the numbers from 0 to 23 and the minutes table with the numbers from 0 to 59. To fill the days table, you can create a procedure like the following:

CREATE PROCEDURE make_days(IN start_date DATE, IN end_date DATE)
BEGIN
  DECLARE curr_date DATE;
  SET curr_date = start_date;
  WHILE curr_date <= end_date DO
    INSERT IGNORE INTO days(day)  VALUES(curr_date);
    SET curr_date = DATE_ADD(curr_date, INTERVAL 1 DAY);
  END WHILE;
END

You can then call this procedure to create days like this:

CALL make_days('2011-01-01','2012-12-31');

Now you can create values for every minute in a given time interval using a query similar to the following:

SELECT YEAR(day) AS year, MONTH(day) AS month, DAYOFMONTH(day) AS day, hour, minute
FROM days, hours, minutes
WHERE CAST(CONCAT(day,' ',hour,':',minute) AS DATETIME) BETWEEN '2011-08-31 22:00' AND '2011-09-01 10:00'
ORDER BY year, month, day, hour, minute