Home/ Questions/Q 8974107
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-15T18:36:22+00:00

I have a database table containing dates when events start. An event ends when

  • 0

I have a database table containing dates when events start. An event ends when the next one starts. Given a start date and end date, I’m looking to create an array of dates with their corresponding event ID.

Currently I run an SQL query for each date. Pseudocode:

$currDate = $startDate
While $currDate++ < $endDate
  echo $currDate . " - " . dbQuery("SELECT TOP 1 ID FROM events WHERE eventDate <= '$currDate' ORDER BY eventDate DESC");
Loop

How can I make this more efficient (in PHP)?

EDIT: Thanks for the answers however I realise the question wasn’t clear. Managed to write some SQL that executes fast (<10ms) on my server for dates spanning years.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Here’s the solution using SQL:

    SQL Fiddle

    MS SQL Server 2008 Schema Setup:

    Create Table dbo.Events (
  ID int not null primary key nonclustered,
  EventDate datetime not null
);


Insert Into dbo.Events (ID, EventDate) Values
  (1, '2011-11-19'),
  (2, '2011-11-25'),
  (3, '2011-12-12'),
  (4, '2012-01-02'),
  (5, '2012-01-05'),
  (6, '2012-02-10');

    Query 1:

    DECLARE @dtStart DATETIME,
        @dtEnd   DATETIME

SET @dtStart = '2011-11-01'
SET @dtEnd = '2012-02-20'

SELECT thedate,
       eventID = (SELECT TOP 1 id
                  FROM   events
                  WHERE  eventdate <= thedate
                  ORDER  BY eventdate DESC)
FROM   (SELECT Dateadd(DAY, number, @dtStart) AS theDate --build dates from the start to end date
        FROM   (SELECT DISTINCT number
                FROM   master.dbo.spt_values
                WHERE  name IS NULL) n --returns integer values from 0 to 2037
        WHERE  Dateadd(DAY, number, @dtStart) < @dtEnd) x

    Results:

    |                         THEDATE | EVENTID |
---------------------------------------------
| November, 01 2011 00:00:00+0000 |  (null) |
| November, 02 2011 00:00:00+0000 |  (null) |
| November, 03 2011 00:00:00+0000 |  (null) |
| November, 04 2011 00:00:00+0000 |  (null) |
| November, 05 2011 00:00:00+0000 |  (null) |
| November, 06 2011 00:00:00+0000 |  (null) |
| November, 07 2011 00:00:00+0000 |  (null) |
| November, 08 2011 00:00:00+0000 |  (null) |
| November, 09 2011 00:00:00+0000 |  (null) |
| November, 10 2011 00:00:00+0000 |  (null) |
| November, 11 2011 00:00:00+0000 |  (null) |
| November, 12 2011 00:00:00+0000 |  (null) |
| November, 13 2011 00:00:00+0000 |  (null) |
| November, 14 2011 00:00:00+0000 |  (null) |
| November, 15 2011 00:00:00+0000 |  (null) |
| November, 16 2011 00:00:00+0000 |  (null) |
| November, 17 2011 00:00:00+0000 |  (null) |
| November, 18 2011 00:00:00+0000 |  (null) |
| November, 19 2011 00:00:00+0000 |       1 |
| November, 20 2011 00:00:00+0000 |       1 |
| November, 21 2011 00:00:00+0000 |       1 |
| November, 22 2011 00:00:00+0000 |       1 |
| November, 23 2011 00:00:00+0000 |       1 |
| November, 24 2011 00:00:00+0000 |       1 |
| November, 25 2011 00:00:00+0000 |       2 |
| November, 26 2011 00:00:00+0000 |       2 |
| November, 27 2011 00:00:00+0000 |       2 |
| November, 28 2011 00:00:00+0000 |       2 |
| November, 29 2011 00:00:00+0000 |       2 |
| November, 30 2011 00:00:00+0000 |       2 |
| December, 01 2011 00:00:00+0000 |       2 |
| December, 02 2011 00:00:00+0000 |       2 |
| December, 03 2011 00:00:00+0000 |       2 |
| December, 04 2011 00:00:00+0000 |       2 |
| December, 05 2011 00:00:00+0000 |       2 |
| December, 06 2011 00:00:00+0000 |       2 |
| December, 07 2011 00:00:00+0000 |       2 |
| December, 08 2011 00:00:00+0000 |       2 |
| December, 09 2011 00:00:00+0000 |       2 |
| December, 10 2011 00:00:00+0000 |       2 |
| December, 11 2011 00:00:00+0000 |       2 |
| December, 12 2011 00:00:00+0000 |       3 |
| December, 13 2011 00:00:00+0000 |       3 |
| December, 14 2011 00:00:00+0000 |       3 |
| December, 15 2011 00:00:00+0000 |       3 |
| December, 16 2011 00:00:00+0000 |       3 |
| December, 17 2011 00:00:00+0000 |       3 |
| December, 18 2011 00:00:00+0000 |       3 |
| December, 19 2011 00:00:00+0000 |       3 |
| December, 20 2011 00:00:00+0000 |       3 |
| December, 21 2011 00:00:00+0000 |       3 |
| December, 22 2011 00:00:00+0000 |       3 |
| December, 23 2011 00:00:00+0000 |       3 |
| December, 24 2011 00:00:00+0000 |       3 |
| December, 25 2011 00:00:00+0000 |       3 |
| December, 26 2011 00:00:00+0000 |       3 |
| December, 27 2011 00:00:00+0000 |       3 |
| December, 28 2011 00:00:00+0000 |       3 |
| December, 29 2011 00:00:00+0000 |       3 |
| December, 30 2011 00:00:00+0000 |       3 |
| December, 31 2011 00:00:00+0000 |       3 |
|  January, 01 2012 00:00:00+0000 |       3 |
|  January, 02 2012 00:00:00+0000 |       4 |
|  January, 03 2012 00:00:00+0000 |       4 |
|  January, 04 2012 00:00:00+0000 |       4 |
|  January, 05 2012 00:00:00+0000 |       5 |
|  January, 06 2012 00:00:00+0000 |       5 |
|  January, 07 2012 00:00:00+0000 |       5 |
|  January, 08 2012 00:00:00+0000 |       5 |
|  January, 09 2012 00:00:00+0000 |       5 |
|  January, 10 2012 00:00:00+0000 |       5 |
|  January, 11 2012 00:00:00+0000 |       5 |
|  January, 12 2012 00:00:00+0000 |       5 |
|  January, 13 2012 00:00:00+0000 |       5 |
|  January, 14 2012 00:00:00+0000 |       5 |
|  January, 15 2012 00:00:00+0000 |       5 |
|  January, 16 2012 00:00:00+0000 |       5 |
|  January, 17 2012 00:00:00+0000 |       5 |
|  January, 18 2012 00:00:00+0000 |       5 |
|  January, 19 2012 00:00:00+0000 |       5 |
|  January, 20 2012 00:00:00+0000 |       5 |
|  January, 21 2012 00:00:00+0000 |       5 |
|  January, 22 2012 00:00:00+0000 |       5 |
|  January, 23 2012 00:00:00+0000 |       5 |
|  January, 24 2012 00:00:00+0000 |       5 |
|  January, 25 2012 00:00:00+0000 |       5 |
|  January, 26 2012 00:00:00+0000 |       5 |
|  January, 27 2012 00:00:00+0000 |       5 |
|  January, 28 2012 00:00:00+0000 |       5 |
|  January, 29 2012 00:00:00+0000 |       5 |
|  January, 30 2012 00:00:00+0000 |       5 |
|  January, 31 2012 00:00:00+0000 |       5 |
| February, 01 2012 00:00:00+0000 |       5 |
| February, 02 2012 00:00:00+0000 |       5 |
| February, 03 2012 00:00:00+0000 |       5 |
| February, 04 2012 00:00:00+0000 |       5 |
| February, 05 2012 00:00:00+0000 |       5 |
| February, 06 2012 00:00:00+0000 |       5 |
| February, 07 2012 00:00:00+0000 |       5 |
| February, 08 2012 00:00:00+0000 |       5 |
| February, 09 2012 00:00:00+0000 |       5 |
| February, 10 2012 00:00:00+0000 |       6 |
| February, 11 2012 00:00:00+0000 |       6 |
| February, 12 2012 00:00:00+0000 |       6 |
| February, 13 2012 00:00:00+0000 |       6 |
| February, 14 2012 00:00:00+0000 |       6 |
| February, 15 2012 00:00:00+0000 |       6 |
| February, 16 2012 00:00:00+0000 |       6 |
| February, 17 2012 00:00:00+0000 |       6 |
| February, 18 2012 00:00:00+0000 |       6 |
| February, 19 2012 00:00:00+0000 |       6 |
    • 0