GROUP_CONCAT() ?
And group by id_fmr ?
JW
On Wed, Sep 29, 2010 at 2:38 PM, Daevid Vincent <daevid@stripped> wrote:
> Given three basic tables. An "fmr" table which has Field Maintenance
> Reports, a Seat table and a "hanging" or "glue" table to map Seats to FMRs.
> [See below]
>
> How do I get all the Seats to be in a single "row" with the FMR data?
>
> If I make this kind of query, they come in as separate rows:
>
> SELECT
> `id_fmr`,
> `fmr_number`,
> `fmr_system`,
> `fmr_station`,
> `created_ts`,
> `seat`
> FROM `fmr`
> JOIN `fmr_has_seat` USING (id_fmr)
> JOIN `dim_seat` USING (id_dim_seat)
> WHERE id_fmr = 3;
>
> id_fmr fmr_number fmr_system fmr_station created_ts seat
> ------ ---------- ---------- ----------- ------------------- ----
> 3 320237274 2333 JFK 2010-09-24 04:35:31 35C
> 3 320237274 2333 JFK 2010-09-24 04:35:31 35D
> 3 320237274 2333 JFK 2010-09-24 04:35:31 35E
>
> I want something more like:
>
> id_fmr fmr_number fmr_system fmr_station created_ts seat
> ------ ---------- ---------- ----------- -------------------
> -----------
> 3 320237274 2333 JFK 2010-09-24 04:35:31
> 35C,35D,35E
>
>
> Now, I'm going to be showing a few thousand FMR rows (and ideally their
> seats).
>
> What I do now is use PHP to pull the FMR records that match a certain
> criteria/filter.
> Then I pull in the entire dim_seats as an array and store it in a session
> since it's not going to change ever. Then I loop over all the id_fmr that I
> have pulled and look up in the fmr_has_seat table by id_fmr and implode()
> the seats from the session array. It saves me a few joins and gets the job
> done, but I keep feeling like there's a better way to do it.
>
> I'm thinking there's some magic with a subselect and concat or something in
> SQL, but then I wonder if that's any more efficient as mySQL still has to
> do two SELECTs per FMR row. This feels to me like a common problem and
> there must be an optimal mySQL way of doing it. Hanging tables of 1:M
> relationships are used everywhere.
>
> ===========================================================================
> ==================
>
> CREATE TABLE `fmr` (
> `id_fmr` int(11) NOT NULL auto_increment,
> `fmr_number` varchar(32) NOT NULL default '',
> `fmr_system` smallint(6) default NULL,
> `fmr_station` varchar(4) NOT NULL default '',
> `created_ts` timestamp NOT NULL default CURRENT_TIMESTAMP,
> PRIMARY KEY (`id_fmr`)
> ) ENGINE=InnoDB
>
> id_fmr fmr_number fmr_system fmr_station created_ts
> ------ ---------- ---------- ----------- -------------------
> 1 319235F2A 2333 JFK 2010-09-24 04:35:31
> 2 319235F29 2333 JFK 2010-09-24 04:35:31
> 3 320237274 2333 JFK 2010-09-24 04:35:31 <---
> 4 32023726D 2333 JFK 2010-09-24 04:35:31
> 5 32023725A 2333 JFK 2010-09-24 04:35:31
> 6 32023724F 2333 JFK 2010-09-24 04:35:31
> 7 320237241 2333 LAX 2010-09-24 04:35:31
> 8 32023723A 2333 LAX 2010-09-24 04:35:31
> 9 320237232 2333 JFK 2010-09-24 04:35:31
> 10 320237230 2333 JFK 2010-09-24 04:35:31
> .. .. .. .. ..
>
> CREATE TABLE `fmr_has_seat` (
> `id_fmr` int(11) NOT NULL auto_increment,
> `id_dim_seat` int(10) unsigned NOT NULL,
> PRIMARY KEY (`id_fmr`,`id_dim_seat`),
> KEY `id_dim_seat` (`id_dim_seat`),
> CONSTRAINT `fmr_has_seat_ibfk_1` FOREIGN KEY (`id_fmr`) REFERENCES `fmr`
> (`id_fmr`) ON DELETE CASCADE ON UPDATE CASCADE,
> CONSTRAINT `fmr_has_seat_ibfk_2` FOREIGN KEY (`id_dim_seat`) REFERENCES
> `dim_seat` (`id_dim_seat`) ON DELETE CASCADE ON UPDATE CASCADE
> ) ENGINE=InnoDB
>
> id_fmr id_dim_seat
> ------ -----------
> 3 888 <---
> 3 889 <---
> 3 890 <---
> 4 422
> 4 423
> 4 551
> 4 552
> 4 553
> 5 420
> 5 550
> 5 628
> 5 629
> 5 706
> 5 707
> 5 811
> ... ...
>
> CREATE TABLE `dim_seat` (
> `id_dim_seat` int(10) unsigned NOT NULL auto_increment,
> `seat` varchar(4) default NULL,
> PRIMARY KEY (`id_dim_seat`),
> KEY `seat` (`seat`)
> ) ENGINE=InnoDB
>
> id_dim_seat seat
> ----------- ------
> ... ...
> 888 35C <---
> 889 35D <---
> 890 35E <---
> 891 35F
> 892 35G
> ... ...
>
>
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>
--
-----------------------------
Johnny Withers
601.209.4985
johnny@stripped
