CODEWITHSUNDEEP
mysql
Raman Ch
Raman Ch

Reputation: 13

Mysql: Query to Join Table Data Based On Closest Timestamp

I have Table in Mysql and I need to be able join the data based on the nearest timestamp in with the matching row [that may be earlier than or equal to or greater than the timestamp[but nearest] of another row based on username].

Here is Sample data Mysql Table:

+----+----------+---------+----------+---------------------+
| Id | userName | Browser | Platform | TS                  |
+----+----------+---------+----------+---------------------+
|  1 | abc      | Firefox | NULL     | 2006-10-05 11:55:45 |
|  2 | xyz      | Chrome  | NULL     | 2007-10-07 12:34:17 |
|  3 | mnp      | Safari  | NULL     | 2008-10-09 08:19:37 |
|  4 | abc      | Safari  | NULL     | 2010-10-13 04:28:14 |
|  5 | abc      | NULL    | Windows  | 2006-01-01 12:02:45 |
|  6 | xyz      | NULL    | Linux    | 2007-01-01 12:01:20 |
|  7 | mnp      | NULL    | MAC      | 2008-01-01 12:02:29 |
|  8 | abc      | NULL    | MAC      | 2010-03-09 13:06:59 |
+----+----------+---------+----------+---------------------+

And I need output like Following:

+----+----------+---------+----------+---------------------+
| Id | userName | Browser | Platform | TS                  |
+----+----------+---------+----------+---------------------+
|  1 | abc      | Firefox | Windows  | 2006-10-05 11:55:45 |
|  2 | xyz      | Chrome  | Linux    | 2007-10-07 12:34:17 |
|  3 | mnp      | Safari  | MAC      | 2008-10-09 08:19:37 |
|  4 | abc      | Safari  | MAC      | 2010-10-13 04:28:14 |
|  5 | abc      | Firefox | Windows  | 2006-01-01 12:02:45 |  
|  6 | xyz      | Chrome  | Linux    | 2007-01-01 12:01:20 |
|  7 | mnp      | Safari  | MAC      | 2008-01-01 12:02:29 |
|  8 | abc      | Safari  | MAC      | 2010-03-09 13:06:59 |
+----+----------+---------+----------+---------------------+

Can Anyone suggest a mysql query needed to get desired output

Upvotes: 1

Views: 225

Answers (2)

Yossi Vainshtein
Yossi Vainshtein

Reputation: 3985

And in case you are in an earlier version of mysql, which doesn't support analytical functions:

(This should be equivalent to the other answer by @Used_By_Already)

SELECT 
  t2.Id, 
  t2.userName, 
  COALESCE(t2.Browser, t2.other_Browser), 
  COALESCE(t2.Platform, t2.other_Platform),
  t2.TS, 
  t2.other_TS
from (

SELECT 
  t.*,
  IF (t.Id = @prev_id, @rankk:=@rankk+1, @rankk:=0) as rankk,
  @prev_id := t.Id
from (
  select 
    a.Id, a.userName, a.Browser , a.Platform, a.TS, 
    b.Id as other_Id, b.Browser as other_Browser , b.Platform as other_Platform, b.TS as other_TS,
    ABS(TIMESTAMPDIFF(SECOND, a.TS, b.TS)) as time_diff
  from mytable a join mytable b on a.userName = b.userName and a.Id <> b.Id
  order by a.Id, ABS(TIMESTAMPDIFF(SECOND, a.TS, b.TS)))
  t join (select @prev_Id:=NULL, @rankk:=0) c
) t2
 WHERE rankk=0

Upvotes: 0

Paul Maxwell
Paul Maxwell

Reputation: 35563

If you have MySQL v8, or MariaDb, that supports lead() over()

CREATE TABLE mytable(
   Id       INT
  ,userName VARCHAR(10)
  ,Browser  VARCHAR(9)
  ,Platform VARCHAR(10)
  ,TS       timestamp
);

INSERT INTO mytable(Id,userName,Browser,Platform,TS) VALUES >     >     >     >     >       (1,'abc','Firefox',NULL,'2006-10-05 11:55:45');
, (2,'xyz','Chrome',NULL,'2007-10-07 12:34:17');
, (3,'mnp','Safari',NULL,'2008-10-09 08:19:37');
, (4,'abc','Safari',NULL,'2010-10-13 04:28:14')
, (5,'abc',NULL,'Windows','2006-01-01 12:02:45')
, (6,'xyz',NULL,'Linux','2007-01-01 12:01:20')
, (7,'mnp',NULL,'MAC','2008-01-01 12:02:29')
, (8,'abc',NULL,'MAC','2010-03-09 13:06:59')

with cte as (
select
*
, coalesce(lead(ts) over(order by ts),current_time) nxt
from mytable
)
select
  id
, username
, coalesce(browser,(select browser from cte where t.ts between cte.ts and cte.nxt limit 1 )) browser
, coalesce(platform,(select platform from cte where t.ts between cte.ts and cte.nxt limit 1 )) platform
, ts
, nxt
from cte t

id | username | browser | platform | ts                  | nxt                
-: | :------- | :------ | :------- | :------------------ | :------------------
 5 | abc      | null    | Windows  | 2006-01-01 12:02:45 | 2006-10-05 11:55:45
 1 | abc      | Firefox | Windows  | 2006-10-05 11:55:45 | 2007-01-01 12:01:20
 6 | xyz      | Firefox | Linux    | 2007-01-01 12:01:20 | 2007-10-07 12:34:17
 2 | xyz      | Chrome  | Linux    | 2007-10-07 12:34:17 | 2008-01-01 12:02:29
 7 | mnp      | Chrome  | MAC      | 2008-01-01 12:02:29 | 2008-10-09 08:19:37
 3 | mnp      | Safari  | MAC      | 2008-10-09 08:19:37 | 2010-03-09 13:06:59
 8 | abc      | Safari  | MAC      | 2010-03-09 13:06:59 | 2010-10-13 04:28:14
 4 | abc      | Safari  | MAC      | 2010-10-13 04:28:14 | 2018-10-02 08:11:44

db<>fiddle here

Upvotes: 2

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