SQLite query to join on a range of dates?

Question

I am working with SQLite.

Suppose I have a table sales with two columns, date and count, to keep track of how many glasses of lemo

Answer 1

You could use a Recursive Common Table expression to generate a series of dates and join to it:

WITH RECURSIVE
  cnt(x) AS (
    SELECT 0
    UNION ALL
    SELECT x+1 FROM cnt
    LIMIT (SELECT ((julianday('2010-01-10') - julianday('2010-01-04'))) + 1)
), 
WITH date_series AS (
  SELECT date(julianday('2010-01-04'), '+' || x || ' days') as date 
FROM date_series ds
)
SELECT AVG(COALESCE(s.count, 0)) as avg_sales_count
FROM date_series ds
  LEFT JOIN sales s ON ds.date = s.date

I wrote a blog post with more info here: http://www.geekytidbits.com/generate-date-range-sqlite/