generate days from date range

Question

I would like to run a query like

select ... as days where `date` is between \'2010-01-20\' and \'2010-01-24\'

And return data like:

Answer 1

The old school solution for doing this without a loop/cursor is to create a NUMBERS table, which has a single Integer column with values starting at 1.

CREATE TABLE  `example`.`numbers` (
  `id` int(10) unsigned NOT NULL auto_increment,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

You need to populate the table with enough records to cover your needs:

INSERT INTO NUMBERS (id) VALUES (NULL);

Once you have the NUMBERS table, you can use:

SELECT x.start_date + INTERVAL n.id-1 DAY
  FROM NUMBERS n
  JOIN (SELECT STR_TO_DATE('2010-01-20', '%Y-%m-%d') AS start_date 
          FROM DUAL) x
 WHERE x.start_date + INTERVAL n.id-1 DAY <= '2010-01-24'

The absolute low-tech solution would be:

SELECT STR_TO_DATE('2010-01-20', '%Y-%m-%d')
 FROM DUAL
UNION ALL
SELECT STR_TO_DATE('2010-01-21', '%Y-%m-%d')
 FROM DUAL
UNION ALL
SELECT STR_TO_DATE('2010-01-22', '%Y-%m-%d')
 FROM DUAL
UNION ALL
SELECT STR_TO_DATE('2010-01-23', '%Y-%m-%d')
 FROM DUAL
UNION ALL
SELECT STR_TO_DATE('2010-01-24', '%Y-%m-%d')
 FROM DUAL

What would you use it for?

---

To generate lists of dates or numbers in order to LEFT JOIN on to. You would to this in order to see where there are gaps in the data, because you are LEFT JOINing onto a list of sequencial data - null values will make it obvious where gaps exist.