I have the following table:
+-----------+-----------+------------+----------+
| id | user_id | start_date | end_date |
| (integer) | (integer) | (date) | (date) |
+-----------+-----------+------------+----------+
Fields start_date
and end_date
are holding date values like YYYY-MM-DD
.
An entry from this table can look like this: (1, 120, 2012-04-09, 2012-04-13)
.
I have to write a query that can fetch all the results matching a certain period.
The problem is that if I want to fetch results from 2012-01-01
to 2012-04-12
, I get 0 results even though there is an entry with start_date = "2012-04-09"
and end_date = "2012-04-13"
.
This question is related to
sql
postgresql
date
overlap
Assuming you want all "overlapping" time periods, i.e. all that have at least one day in common.
Try to envision time periods on a straight time line and move them around before your eyes and you will see the necessary conditions.
SELECT *
FROM tbl
WHERE start_date <= '2012-04-12'::date
AND end_date >= '2012-01-01'::date;
This is sometimes faster for me than OVERLAPS
- which is the other good way to do it (as @Marco already provided).
Note the subtle difference (per documentation):
OVERLAPS
automatically takes the earlier value of the pair as the start. Each time period is considered to represent the half-open intervalstart <= time < end
, unless start and end are equal in which case it represents that single time instant. This means for instance that two time periods with only an endpoint in common do not overlap.
Bold emphasis mine.
For big tables the right index can help performance (a lot).
CREATE INDEX tbl_date_inverse_idx ON tbl(start_date, end_date DESC);
Possibly with another (leading) index column if you have additional selective conditions.
Note the inverse order of the two columns. Detailed explanation:
Looking at the dates for which it doesn't work -- those where the day is less than or equal to 12 -- I'm wondering whether it's parsing the dates as being in YYYY-DD-MM format?
just had the same question, and answered this way, if this could help.
select *
from table
where start_date between '2012-01-01' and '2012-04-13'
or end_date between '2012-01-01' and '2012-04-13'
No offense but to check for performance of sql I executed some of the above mentioned solutiona pgsql.
Let me share you Statistics of top 3 solution approaches that I come across.
1) Took : 1.58 MS Avg
2) Took : 2.87 MS Avg
3) Took : 3.95 MS Avg
Now try this :
SELECT * FROM table WHERE DATE_TRUNC('day', date ) >= Start Date AND DATE_TRUNC('day', date ) <= End Date
Now this solution took : 1.61 Avg.
And best solution is 1st that suggested by marco-mariani
You have to use the date part fetching method:
SELECT * FROM testbed WHERE start_date ::date >= to_date('2012-09-08' ,'YYYY-MM-DD') and date::date <= to_date('2012-10-09' ,'YYYY-MM-DD')
SELECT *
FROM ecs_table
WHERE (start_date, end_date) OVERLAPS ('2012-01-01'::DATE, '2012-04-12'::DATE + interval '1');
To have a query working in any locale settings, consider formatting the date yourself:
SELECT *
FROM testbed
WHERE start_date >= to_date('2012-01-01','YYYY-MM-DD')
AND end_date <= to_date('2012-04-13','YYYY-MM-DD');
Source: Stackoverflow.com