Re: aggregate query

"Andrew Kroeger" <andrew(at)sprocks(dot)gotdns(dot)com> writes:

> Raj A wrote:
>> I have a table
>>
>> CREATE TABLE survey_load
>> (
>> meter_id character(5) NOT NULL,
>> number_of_bays integer NOT NULL,
>> bay_1_use integer,
>> bay_2_use integer,
>> bay_3_use integer,
>> bay_4_use integer,
>> bay_5_use integer,
>> date date NOT NULL,
>> inspection_id integer NOT NULL DEFAULT,
>> )
>>
>> How do i present an aggregate query
>>
>> inspection_id | meter_id | bay_use
>> 1 12345 (value of bay_1_use)
>> 1 12345 (value of bay_2_use)
>> 1 12345 (value of bay_3_use)
>> 2 23456 (value of bay_1_use)
>> 2 23456 (value of bay_2_use)
>> 2 23456 (value of bay_3_use)
>> 2 23456 (value of bay_4_use)
>> 2 23456 (value of bay_5_use)

>
> If I understand your issue correctly, it seems like the denormalized
> nature of your table is causing you some problems.

True. Normalizing the tables would make this query easier which is a good sign
that that's probably the right direction.

If for some reason you can't or won't change the table definition there are a
number of possible tricky answers given the current definition. Something like
this for example:

SELECT inspection_id, meter_id,
case when bay=1 then bay_1_use
when bay=2 then bay_2_use
when bay=3 then bay_3_use
when bay=4 then bay_4_use
when bay=5 then bay_5_use
else null
end AS bay_use
FROM (
SELECT *, generate_series(1,number_of_bays) AS bay
FROM survey_load
) as x

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com