Advanced SQL Select and Union Statements - sql

Question

I've seen other similar questions and I have tried implementing many solutions, but to to no avail so far. This specific questions involves a little more complexity. What I need to do is create a table and join columns to the right side depending on certain criterion. It seems simple enough, but there are a few bumps that I am encountering.
The tables are as follows:
ADC_DATA_COLLECTION_HEADER
(PK)Transaction_ID | BEMSID | DEVICE | TIMESTAMP | CONFIG_NAME
ADC_DATA_COLLECTION_APPS
(FK)CONFIG_NAME | NUM_DATA_ELEMENTS | DATA_ELEMENT1 | DATA_ELEMENT2 | DATA_ELEMENT3 | DATA_ELEMENT4
ADC_DATA_COLLECTION_DATA
(FK)TRANSACTION_ID | DATA_ELEMENT_NUMBER | DATA
I want my final output to look like:
TRANSACTION_ID | DEVICE | CONFIG_NAME | DATA | DATA | DATA | DATA
The "data" column is filled in using the table ADC_DATA_COLLECTION_DATA. The first instance of "data" would be the "data" field in ADC_DATA_COLLECTION_DATA where DATA_ELEMENT_NUMBER = 1. The second instance of "data" would be the "data" field in ADC_DATA_COLLECTION_DATA where DATA_ELEMENT_NUMBER = 2... And so on.
The furthest I have gotten is by using a join statement, except I have nulls in places I do not want them. The code I have used and the results are posted below. So far I only wrote code for the first two columns of data.
SELECT
ADC_Data_Collection_header.BEMSID,
ADC_Data_Collection_header.DEVICE,
ADC_Data_Collection_header.CONFIG_NAME,
null AS locationlabel,
null AS partno
/*null AS partno2,
null AS DE4,
null AS DE5,
null AS DE6 */
FROM
ADC_Data_Collection_header,
ADC_Data_Collection_apps,
ADC_Data_Collection_data
WHERE
ADC_Data_Collection_header.CONFIG_NAME = 'mobileScanning'
AND ADC_Data_Collection_header.BEMSID = '2386531'
AND ADC_Data_Collection_header.CONFIG_NAME = ADC_Data_Collection_apps.CONFIG_NAME
AND (TO_DATE('7/19/2013','MM/DD/YYYY') <= timestamp AND TO_DATE('7/27/2013','MM/DD/YYYY') >= timestamp)
AND ADC_DATA_COLLECTION_HEADER.transaction_ID = ADC_DATA_COLLECTION_DATA.Transaction_ID
UNION
SELECT
null as BEMSID,
null as DEVICE,
null as CONFIG_NAME,
ADC_Data_Collection_DATA.DATA AS locationlabel,
null as partno
FROM
ADC_DATA_COLLECTION_DATA,
ADC_Data_Collection_header,
ADC_Data_Collection_apps
WHERE
ADC_DATA_COLLECTION_DATA.DATA_ELEMENT_NUMBER = 3
AND ADC_Data_Collection_header.CONFIG_NAME = 'mobileScanning'
AND (TO_DATE('7/19/2013','MM/DD/YYYY') <= timestamp AND TO_DATE('7/27/2013','MM/DD/YYYY') >= timestamp)
AND ADC_DATA_COLLECTION_HEADER.transaction_ID = ADC_DATA_COLLECTION_DATA.Transaction_ID
UNION
SELECT
null as BEMSID,
null as DEVICE,
null as CONFIG_NAME,
null as locationlabel,
ADC_Data_Collection_DATA.DATA AS partno
FROM
ADC_DATA_COLLECTION_DATA,
ADC_Data_Collection_header,
ADC_Data_Collection_apps
WHERE
ADC_DATA_COLLECTION_DATA.DATA_ELEMENT_NUMBER = 4
AND ADC_Data_Collection_header.CONFIG_NAME = 'mobileScanning'
AND (TO_DATE('7/19/2013','MM/DD/YYYY') <= timestamp AND TO_DATE('7/27/2013','MM/DD/YYYY') >= timestamp)
AND ADC_DATA_COLLECTION_HEADER.transaction_ID = ADC_DATA_COLLECTION_DATA.Transaction_ID
The result from this appears with null values which I do not want to have.
If you can offer an explicit solution using a join statement or a fix to this union approach, it would be much appreciated. Thank you in advance!

Answer 1

UNION gives you additional rows so it's not the right tool for this situation.
Here's an abbreviated version that uses your ADC_DATA_COLLECTION_DATA table only; you should be able to incorporate this into your query:
SELECT
Transaction_ID,
MAX(CASE WHEN Data_Element_Number = 1 THEN Data END) AS Data1,
MAX(CASE WHEN Data_Element_Number = 2 THEN Data END) AS Data2,
MAX(CASE WHEN Data_Element_Number = 3 THEN Data END) AS Data3,
MAX(CASE WHEN Data_Element_Number = 4 THEN Data END) AS Data4
FROM ADC_DATA_COLLECTION_DATA
GROUP BY Transaction_ID
This is a fairly common "Pivot Table" hack for Oracle (and MySQL and SQL Server). Oracle also supports PIVOT queries but I'm not that good with them.
Note that once you put your final query together with the Device and Config_Name columns, you'll need to add those columns to your GROUP BY.

Answer 2

I would use pivot for this:
select
h.transaction_id,
h.device,
h.config_name,
d.data1,
d.data2,
d.data3,
d.data4
from
ADC_DATA_COLLECTION_HEADER h
inner join (
select *
from ADC_DATA_COLLECTION_DATA
pivot
(
max(data)
for data_element_number in (1 as data1, 2 as data2, 3 as data3, 4 as data4)
)
) d
on d.transaction_id = h.transaction_id
where
(TO_DATE('7/19/2013','MM/DD/YYYY') <= timestamp AND TO_DATE('7/27/2013','MM/DD/YYYY') >= timestamp);
I put together an example SQL Fiddle at: http://www.sqlfiddle.com/#!4/fe1c94/9/0