Creating a date range table

Question

I'm writing a report that needs to display a value per day. I have the start and end date for the query, but I wish to avoid missing days in case the table does not contain a value for a specific date. I was thinking about creating a base date range table that holds all days between start and end, then left join it with the data table to show a value for each day.

I found a few scripts for mySQL, SQL Server, etc.. but none for SQLite. Is there a way to quickly populate a table with a date range?

Thanks

Answer 1

Here's how you could use a numbers table to expand a range:

SELECT
  datetime('now', N || ' seconds') AS DT
FROM numbers
WHERE N < strftime('%s', 'now', '1 minutes') - strftime('%s', 'now');

In this case, the numbers table is supposed to hold numbers starting from 0.

A numbers table is a tool worth keeping handy for many purposes. You could initialise it like this, for instance:

CREATE TABLE numbers (N int);
/* #0 */ INSERT INTO numbers (N) SELECT 0;
/* #1 */ INSERT INTO numbers (N) SELECT N + C FROM numbers, (SELECT COUNT(*) AS C FROM numbers);
/* #2 */ INSERT INTO numbers (N) SELECT N + C FROM numbers, (SELECT COUNT(*) AS C FROM numbers);
/* #3 */ INSERT INTO numbers (N) SELECT N + C FROM numbers, (SELECT COUNT(*) AS C FROM numbers);
/* #4 */ INSERT INTO numbers (N) SELECT N + C FROM numbers, (SELECT COUNT(*) AS C FROM numbers);
/* #5 */ INSERT INTO numbers (N) SELECT N + C FROM numbers, (SELECT COUNT(*) AS C FROM numbers);
/* #6 */ INSERT INTO numbers (N) SELECT N + C FROM numbers, (SELECT COUNT(*) AS C FROM numbers);
/* #… */

Every line # N results in 2 ^N rows in the table, the largest number being 2 N -1

A demonstration of the method can be found (and played with) on SQL Fiddle .

Answer 2

it depends the level of details you want. If you simply want the dates from A until B you can do this:

declare @start datetime
set @start = '04/20/2012'
while @start <getdate() begin
  print @start
  set @start = dateadd(dd,1,@start)
end

just change the print to a insert on a table.

If you need more details you may need a more elaborate scripts. I can point you to some, just be more specific on your requirements