SQL Query: Search with list of tuples - sql

Question

I have a following table (simplified version) in SQLServer.
Table Events
-----------------------------------------------------------
| Room | User | Entered | Exited |
-----------------------------------------------------------
| A | Jim | 2014-10-10T09:00:00 | 2014-10-10T09:10:00 |
| B | Jim | 2014-10-10T09:11:00 | 2014-10-10T09:22:30 |
| A | Jill | 2014-10-10T09:00:00 | NULL |
| C | Jack | 2014-10-10T09:45:00 | 2014-10-10T10:00:00 |
| A | Jack | 2014-10-10T10:01:00 | NULL |
.
.
.
I need to create a query that returns person's whereabouts in given timestamps.
For an example: Where was (Jim at 2014-10-09T09:05:00), (Jim at 2014-10-10T09:01:00), (Jill at 2014-10-10T09:10:00), ...
The result set must contain the given User and Timestamp as well as the found room (if any).
------------------------------------------
| User | Timestamp | WasInRoom |
------------------------------------------
| Jim | 2014-10-09T09:05:00 | NULL |
| Jim | 2014-10-09T09:01:00 | A |
| Jim | 2014-10-10T09:10:00 | A |
The number of User-Timestamp tuples can be > 10 000.
The current implementation retrieves all records from Events table and does the search in Java code. I am hoping that I could push this logic to SQL. But how?
I am using MyBatis framework to create SQL queries so the tuples can be inlined to the query.

Answer 1

The basic query is:
select e.*
from events e
where e.user = 'Jim' and '2014-10-09T09:05:00' >= e.entered and ('2014-10-09T09:05:00' <= e.exited or e.exited is NULL) or
e.user = 'Jill' and '2014-10-10T09:10:00 >= e.entered and ('2014-10-10T09:10:00' <= e.exited or e.exited is NULL) or
. . .;
SQL Server can handle ridiculously large queries, so you can continue in this vein. However, if you have the name/time values in a table already (or it is the result of a query), then use a join:
select ut.*, t.*
from usertimes ut left join
events e
on e.user = ut.user and
ut.thetime >= et.entered and (ut.thetime <= exited or ut.exited is null);
Note the use of a left join here. It ensures that all the original rows are in the result set, even when there are no matches.

Answer 2

Answers from Jonas and Gordon got me on track, I think.
Here is query that seems to do the job:
CREATE TABLE #SEARCH_PARAMETERS(User VARCHAR(16), "Timestamp" DATETIME)
INSERT INTO #SEARCH_PARAMETERS(User, "Timestamp")
VALUES
('Jim', '2014-10-09T09:05:00'),
('Jim', '2014-10-10T09:01:00'),
('Jill', '2014-10-10T09:10:00')
SELECT #SEARCH_PARAMETERS.*, Events.Room FROM #SEARCH_PARAMETERS
LEFT JOIN Events
ON #SEARCH_PARAMETERS.User = Events.User AND
#SEARCH_PARAMETERS."Timestamp" > Events.Entered AND
(Events.Exited IS NULL OR Events.Exited > #SEARCH_PARAMETERS."Timestamp"
DROP TABLE #SEARCH_PARAMETERS

Answer 3

By declaring a table valued parameter type for the (user, timestamp) tuples, it should be simple to write a table valued user defined function which returns the desired result by joining the parameter table and the Events table. See http://msdn.microsoft.com/en-us/library/bb510489.aspx
Since you are using MyBatis it may be easier to just generate a table variable for the tuples inline in the query and join with that.