IBM DB2: Generate list of dates between two dates

Question

I need a query which will output a list of dates between two given dates.

For example, if my start date is 23/02/2016 and end date is 02/03/2016, I am expecting the following output:

Date
----
23/02/2016
24/02/2016
25/02/2016
26/02/2016
27/02/2016
28/02/2016
29/02/2016
01/03/2016
02/03/2016

Also, I need the above using SQL only (without the use of 'WITH' statement or tables). Please help.

Answer 1

I am using ,ostly DB2 for iSeries, so I will give you an SQL only solution that works on it. Currently I don't have an access to the server, so the query is not tested but it should work. EDIT Query is already tested and working

SELECT
    d.min + num.n DAYS
FROM
    -- create inline table with min max date
    (VALUES(DATE('2015-02-28'), DATE('2016-03-01'))) AS d(min, max)
INNER JOIN
    -- create inline table with numbers from 0 to 999
    (
        SELECT
            n1.n + n10.n + n100.n AS n
        FROM
            (VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) AS n1(n)
        CROSS JOIN
            (VALUES(0),(10),(20),(30),(40),(50),(60),(70),(80),(90)) AS n10(n)
        CROSS JOIN
            (VALUES(0),(100),(200),(300),(400),(500),(600),(700),(800),(900)) AS n100(n)
    ) AS num
ON
    d.min + num.n DAYS<= d.max
ORDER BY
    num.n;

if you don't want to execute the query only once, you should consider creating a real table with values for the loop:

CREATE TABLE dummy_loop AS (
    SELECT
        n1.n + n10.n + n100.n AS n
    FROM
        (VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) AS n1(n)
    CROSS JOIN
        (VALUES(0),(10),(20),(30),(40),(50),(60),(70),(80),(90)) AS n10(n)
    CROSS JOIN
        (VALUES(0),(100),(200),(300),(400),(500),(600),(700),(800),(900)) AS n100(n)
) WITH DATA;

ALTER TABLE dummy_loop ADD PRIMARY KEY (dummy_loop.n);

It depends on the reason for which you like to use it, but you could even create table for lets say for 100 years. It will be only 100*365 = 36500 rows with just a date field, so the table will be quite small and fast for joins.

CREATE TABLE dummy_dates AS (
    SELECT
        DATE('1970-01-01') + (n1.n + n10.n + n100.n) DAYS AS date
    FROM
        (VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) AS n1(n)
    CROSS JOIN
        (VALUES(0),(10),(20),(30),(40),(50),(60),(70),(80),(90)) AS n10(n)
    CROSS JOIN
        (VALUES(0),(100),(200),(300),(400),(500),(600),(700),(800),(900)) AS n100(n)
) WITH DATA;

ALTER TABLE dummy_dates ADD PRIMARY KEY (dummy_dates.date);

And the select query could look like:

SELECT
    *
FROM
    dummy_days
WHERE
    date BETWEEN(:startDate, :endDate);

EDIT 2: Thanks to @Lennart suggestion I have changed TABLE(VALUES(..,..,..)) to VALES(..,..,..) because as he said TABLE is a synonym to LATERAL that was a real surprise for me.

EDIT 3: Thanks to @godric7gt I have removed TIMESTAMPDIFF and will remove from all my scripts, because as it is said in the documentation:

These assumptions are used when converting the information in the second argument, which is a timestamp duration, to the interval type specified in the first argument. The returned estimate may vary by a number of days. For example, if the number of days (interval 16) is requested for the difference between '1997-03-01-00.00.00' and '1997-02-01-00.00.00', the result is 30. This is because the difference between the timestamps is 1 month, and the assumption of 30 days in a month applies.

It was a real surprise, because I was always trust this function for days difference.

Answer 2

For generating rows recusive SQL will needed. Usually this looks like this in DB2:

with temp (date) as (
select date('23.02.2016') as date from sysibm.sysdummy1
union all
select date + 1 day from temp
where date < date('02.03.2016') 
)

select * from temp

For whatever reason a CTE (using WITH) should be avoided. A possible workaround would be setting

db2set DB2_COMPATIBILITY_VECTOR=8

which enables the use of the Oracle style recusion with CONNECT BY

SELECT date('22.02.2016') + level days  as dt
  FROM sysibm.sysdummy1 CONNECT BY date('22.02.2016') + level days <= date('02.03.2016')

Please note: after setting the DB2_COMPATIBILITY_VECTOR a instance restart is necessary.