Compare multiple date ranges - sql

Question

I am using iReport 3.0.0, PostgreSQL 9.1. For a report I need to compare date ranges from invoices with date ranges in filters and print for every invoice code if a filter range is covered, partially covered, etc. To complicate things, there can be multiple date ranges per invoice code.
Table Invoices
ID Code StartDate EndDate
1 111 1.5.2012 31.5.2012
2 111 1.7.2012 20.7.2012
3 111 25.7.2012 31.7.2012
4 222 1.4.2012 15.4.2012
5 222 18.4.2012 30.4.2012
Examples
Filter: 1.5.2012. - 5.6.2012.
Result that I need to get is:
code 111 - partialy covered
code 222 - invoice missing
Filter: 1.5.2012. - 31.5.2012.
code 111 - fully covered
code 222 - invoice missing
Filter: 1.6.2012. - 30.6.2012.
code 111 - invoice missing
code 222 - invoice missing

Answer 1

After clarification in comment.
Your task as I understand it:
Check for all supplied individual date ranges (filter) whether they are are covered by the combined date ranges of sets of codes in your table (invoice).
It can be done with plain SQL, but it is not a trivial task. The steps could be:
Supply date ranges as filters.
Combine date ranges in invoice table per code.
Can result in one or more ranges per code.
Look for overlaps between filters and combined invoices
Classify: fully covered / partially covered.
Can result in one full coverage, one or two partial coverages or no coverage.
Reduce to maximum level of coverage.
Display one row for every combination of (filter, code) with the resulting coverage, in a sensible sort order
Ad hoc filter ranges
WITH filter(filter_id, startdate, enddate) AS (
VALUES
(1, '2012-05-01'::date, '2012-06-05'::date) -- list filters here.
,(2, '2012-05-01', '2012-05-31')
,(3, '2012-06-01', '2012-06-30')
)
SELECT * FROM filter;
Or put them in a (temporary) table and use the table instead.
Combine overlapping / adjacent date ranges per code
WITH a AS (
SELECT code, startdate, enddate
,max(enddate) OVER (PARTITION BY code ORDER BY startdate) AS max_end
-- Calculate the cumulative maximum end of the ranges sorted by start
FROM invoice
), b AS (
SELECT *
,CASE WHEN lag(max_end) OVER (PARTITION BY code
ORDER BY startdate) + 2 > startdate
-- Compare to the cumulative maximum end of the last row.
-- Only if there is a gap, start a new group. Therefore the + 2.
THEN 0 ELSE 1 END AS step
FROM a
), c AS (
SELECT code, startdate, enddate, max_end
,sum(step) OVER (PARTITION BY code ORDER BY startdate) AS grp
-- Members of the same date range end up in the same grp
-- If there is a gap, the grp number is incremented one step
FROM b
)
SELECT code, grp
,min(startdate) AS startdate
,max(enddate) AS enddate
FROM c
GROUP BY 1, 2
ORDER BY 1, 2
Alternative final SELECT (may be faster or not, you'll have to test):
SELECT DISTINCT code, grp
,first_value(startdate) OVER w AS startdate
,last_value(enddate) OVER w AS enddate
FROM c
WINDOW W AS (PARTITION BY code, grp ORDER BY startdate
RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
ORDER BY 1, 2;
Combine to one query
WITH
-- supply one or more filter values
filter(filter_id, startdate, enddate) AS (
VALUES
(1, '2012-05-01'::date, '2012-06-05'::date) -- cast values in first row
,(2, '2012-05-01', '2012-05-31')
,(3, '2012-06-01', '2012-06-30')
)
-- combine date ranges per code
,a AS (
SELECT code, startdate, enddate
,max(enddate) OVER (PARTITION BY code ORDER BY startdate) AS max_end
FROM invoice
), b AS (
SELECT *
,CASE WHEN (lag(max_end) OVER (PARTITION BY code ORDER BY startdate)
+ 2) > startdate THEN 0 ELSE 1 END AS step
FROM a
), c AS (
SELECT code, startdate, enddate, max_end
,sum(step) OVER (PARTITION BY code ORDER BY startdate) AS grp
FROM b
), i AS ( -- substitutes original invoice table
SELECT code, grp
,min(startdate) AS startdate
,max(enddate) AS enddate
FROM c
GROUP BY 1, 2
)
-- match filters
, x AS (
SELECT f.filter_id, i.code
,bool_or(f.startdate >= i.startdate
AND f.enddate <= i.enddate) AS full_cover
FROM filter f
JOIN i ON i.enddate >= f.startdate
AND i.startdate <= f.enddate -- only overlapping
GROUP BY 1,2
)
SELECT f.*, i.code
,CASE x.full_cover
WHEN TRUE THEN 'fully covered'
WHEN FALSE THEN 'partially covered'
ELSE 'invoice missing'
END AS covered
FROM (SELECT DISTINCT code FROM i) i
CROSS JOIN filter f -- all combinations of filter and code
LEFT JOIN x USING (filter_id, code) -- join in overlapping
ORDER BY filter_id, code;
Tested and works for me on PostgreSQL 9.1.