[vox-tech] puzzling over MySQL query: joining aggregated values in a single query

[Dylan Beaudette]

Hi!

I have a simple table with multiple records per id number: soil horizons from 
numerous pits. the top and bottom of each horizon or layer is defined in the 
fields 'top' and 'bottom'

a quick example of a single pit's records would like like this:
+---------------------+-----------+------+------+--------+
| pedon_id            | hz_number | name | top  | bottom |
+---------------------+-----------+------+------+--------+
| SSGG-spring-05-P009 |         1 | O    |    0 |      3 |
| SSGG-spring-05-P009 |         2 | A1   |    3 |     14 |
| SSGG-spring-05-P009 |         3 | A2   |   14 |     26 |
| SSGG-spring-05-P009 |         4 | AB   |   26 |     70 |
| SSGG-spring-05-P009 |         5 | Bw1  |   70 |    108 |
| SSGG-spring-05-P009 |         6 | Bw2  |  108 |    145 |
| SSGG-spring-05-P009 |         7 | 2C   |  145 |    170 |
| SSGG-spring-05-P009 |         8 | 3Ab  |  170 |    226 |
| SSGG-spring-05-P009 |         9 | 3Bwb |  226 |    240 |
+---------------------+-----------+------+------+--------+


I am able to select out the soil depth, excluding certain horizons with the 
following query:

select pedon_id, max(bottom) as depth from horizon where name REGEXP '.?C.?|
R|.b.?' != 1 group by pedon_id ; 

a simple result for the above example would be:
+---------------------+-------+
| pedon_id            | depth |
+---------------------+-------+
| SSGG-spring-05-P009 |   145 |
+---------------------+-------+

This works well, except for when I would like to join this aggregated 
information to a new table in a single query. Is it possible to do something 
like this:

pseudo-SQL;

select table_a.* , (pedon_id, max(bottom) as depth from horizon where name 
REGEXP '.?C.?|R|.b.?' != 1 group by pedon_id) from table_a, horizon 
where ....

i.e. is it possible to perform an aggregation in the same step as the join, or 
am I going to need to use some temp. tables?

Any thoughts -- am i trying to do something completely ridiculous?

Thanks!





-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341