TERADATA: query optimization - sql

Question

This query is working but it seems to take longer time than usual to retrieve the data. Is there a better solution to optimize this query? I need to get all PRD_ID from T1 and T2 even if there is no match with S1 and S2.
SELECT DISTINCT T.PRD_ID T.AMOUNT, T.DATE, T.REGION
FROM
(
SELECT DISTINCT T1.PRD_ID, T1.PRD_CODE, S1.ORDER_DATE AS DATE, T1.REGION
FROM
(
(SELECT PRD_ID, PRD_CODE,AMOUNT,REGION
FROM PRODUCT
WHERE REGION='CA') T1
LEFT JOIN SERVICE_1 S1
ON S1.PRD_ID = T1.PRD_ID
AND S1.PRD_CODE= T1.PRD_CODE
AND S1.AMT = T1.AMOUNT
AND S1.ORDER_DATE >= '01/01/2015'
AND S1.ORDER_DATE <= '02/28/2015'
)
UNION ALL
SELECT DISTINCT T2.PRD_ID, T2.PRD_CODE, S2.ACCT_CALENDAR_DT AS DATE, T2.REGION
FROM
(
(SELECT PRD_ID, PRD_CODE,AMOUNT,REGION
FROM PRODUCT
WHERE REGION='IL') T2
LEFT JOIN SERVICE_2 S2
ON S2.PRD_ID = T2.PRD_ID
AND S2.PRD_CODE= T2.PRD_CODE
AND S2.AMT = T2.AMOUNT
AND S2.ACCT_CALENDAR_DT >= '20150101'
AND S2.ACCT_CALENDAR_DT <= '20150228'
)
) T
ORDER BY REGION, ORDER_DATE DESC, PRD_ID

Answer 1

I can't see why you need all these (3!) levels of nested tables. The following should be equivalent:
SELECT DISTINCT
T1.PRD_ID, T1.PRD_CODE, S1.ORDER_DATE AS DATE, T1.REGION
FROM
PRODUCT T1
LEFT JOIN SERVICE_1 S1
ON S1.PRD_ID = T1.PRD_ID
AND S1.PRD_CODE= T1.PRD_CODE
AND S1.AMT = T1.AMOUNT
AND S1.ORDER_DATE >= DATE '2015-01-01' -- converted '01/01/2015'
AND S1.ORDER_DATE <= DATE '2015-02-28' -- converted '02/28/2015'
WHERE T1.REGION = 'CA'
UNION ALL -- No need for DISTINCT here. The Region
-- is different between the 2 parts.
SELECT DISTINCT
T2.PRD_ID, T2.PRD_CODE, S2.ACCT_CALENDAR_DT AS DATE, T2.REGION
FROM
PRODUCT T2
LEFT JOIN SERVICE_2 S2
ON S2.PRD_ID = T2.PRD_ID
AND S2.PRD_CODE= T2.PRD_CODE
AND S2.AMT = T2.AMOUNT
AND S2.ACCT_CALENDAR_DT >= DATE '2015-01-01'
AND S2.ACCT_CALENDAR_DT <= DATE '2015-02-28'
WHERE T2.REGION = 'IL'
ORDER BY REGION, DATE DESC, PRD_ID ;
or:
SELECT DISTINCT
T1.PRD_ID, T1.PRD_CODE, S1.ORDER_DATE AS DATE, 'CA' AS REGION
FROM
( SELECT PRD_ID, PRD_CODE, AMOUNT
FROM PRODUCT
WHERE REGION = 'CA'
) T1
LEFT JOIN SERVICE_1 S1
ON S1.PRD_ID = T1.PRD_ID
AND S1.PRD_CODE= T1.PRD_CODE
AND S1.AMT = T1.AMOUNT
AND S1.ORDER_DATE >= DATE '2015-01-01'
AND S1.ORDER_DATE <= DATE '2015-02-28'
UNION ALL
SELECT DISTINCT
T2.PRD_ID, T2.PRD_CODE, S2.ACCT_CALENDAR_DT AS DATE, 'IL' AS REGION
FROM
( SELECT PRD_ID, PRD_CODE, AMOUNT
FROM PRODUCT
WHERE REGION = 'IL'
) T2
LEFT JOIN SERVICE_2 S2
ON S2.PRD_ID = T2.PRD_ID
AND S2.PRD_CODE= T2.PRD_CODE
AND S2.AMT = T2.AMOUNT
AND S2.ACCT_CALENDAR_DT >= DATE '2015-01-01'
AND S2.ACCT_CALENDAR_DT <= DATE '2015-02-28'
ORDER BY REGION, DATE DESC, PRD_ID ;