SQL/Mysql Query available dates in database - mysql

Question

I need some help querying my calendar/dates table
Scenario:
I have a "calendar" table with dates, user will set his available dates, usually day by day. So my table looks like this:
+------+------------+---------------------+---------------------+
| ID | user_id | start_date | end_date |
+------+------------+---------------------+---------------------+
| 1 | 1 | 2016-09-01 08:00:00 | 2016-09-01 16:00:00 |
| 2 | 1 | 2016-09-03 08:00:00 | 2016-09-03 16:00:00 |
| 3 | 1 | 2016-09-04 08:00:00 | 2016-09-04 16:00:00 |
| 3 | 1 | 2016-09-05 08:00:00 | 2016-09-05 16:00:00 |
+------+------------+---------------------+---------------------+
This means user 1 is available on the 1st, 3rd, 4th and 5th.
Lets say I want to query the table and find if user is available from date 2016-09-01 08:00:00 to 2016-09-05 16:00:00, this query must return zero rows since the user is not available on the 2nd of September. But if query from date 2016-09-03 08:00:00 to 2016-09-05 16:00: 00 then it will return these 3 rows.
Hope someone can help me with this

Answer 1

This could be one way (for a single user).
Note #endDate and #startDate are the supplied date fields to search.
SELECT
*
FROM your_table
WHERE EXISTS (
SELECT
user_id
FROM your_table
WHERE start_date >= #startDate
AND start_date <= #endDate
AND user_id = 1
GROUP BY user_id
HAVING SUM((DATEDIFF(end_date,start_date)+1)) = DATEDIFF(#endDate,#startDate)+1
)
AND start_date >= #startDate
AND start_date <= #endDate
AND user_id = 1
Note:
If the supplied date range falls within any range bounded by start_date and end_date (exclusive) then it won't work.
Since SUM((DATEDIFF(end_date,start_date)+1)) = DATEDIFF(#endDate,#startDate)+1 won't be equal in this case. Condition
In this case, you need to stay within the required boundary. Here the boundary is demarcated by the smaller value of end_date and #endDate and the larger value of start_date and #startDate.
Suppose, you have the following record (only one)
start_date = 2016-09-01 and end_date=2016-09-05.
And #startDate=2016-09-02 , #endDate=2016-09-04
Now check the above condition will fail for this set of data.
In this case you need to adopt the following query:
SELECT
*
FROM your_table
WHERE EXISTS (
SELECT
user_id
FROM your_table
WHERE end_date >= #startDate
AND start_date <= #endDate
AND user_id = 1
GROUP BY user_id
HAVING SUM((DATEDIFF(LEAST(end_date,#endDate),GREATEST(start_date,#startDate))+1)) = DATEDIFF(#endDate,#startDate)+1
)
AND end_date >= #startDate
AND start_date <= #endDate
AND user_id = 1

Answer 2

Assuming the periods in the table are not overlapping, you can count the number of days. The days in the period are then:
select sum(datediff(least($period_end, end_date),
greatest($period_start, start_date)
) + 1
)
from t
where $period_start <= end_date and
$period_end >= start_date;
You can then get a flag by comparing to the number of days:
select (case when sum(datediff(least($period_end, end_date),
greatest($period_start, start_date)
) + 1
) =
datediff($period_end, $period_start) + 1
then 1 else 0
end) as IsAvailableForAllDays
from t
where $period_start <= end_date and
$period_end >= start_date;