SQL query to remove these duplicates - sql

Question

So I have no experience in SQL but I have no resource to use for identifying duplicates.
The problem: A SER_NO(serial #) can show up on 2 different dates (EVENT_TS), and I only want to see the first occurrence the SER_NO shows up.
If I have the choice, I would keep the date that the SER_NO showed up on, and not any other date after, but at this point, I just don't want to see duplicate SER_NO
I went the SELECT DISTINCT route and that doesn't help... I need to identify if the SER_NO occurs more than once, and then if it does, I aim to keep the first occurrence (MIN DATE).
SELECT
EVENT_TS, EVENT_NO, FAC_PROD_FAM_CD, SER_NO, DISC_AREA_ID, DISC_AREA_DESC,
QUALITY_VELOCITY, CMPNT_SERIAL_NO, PROTOTYPE_IND, EXT_CPY_STAT
FROM ABUS_DW.V_BIQ_R8_QWB_EVENTS
WHERE
(FAC_PROD_FAM_CD='ACOM' OR FAC_PROD_FAM_CD='SCOM' OR FAC_PROD_FAM_CD='LAP' OR
FAC_PROD_FAM_CD='RM' OR FAC_PROD_FAM_CD='SCRD')
AND (DISC_AREA_ID='400' OR DISC_AREA_ID='450')
AND PROTOTYPE_IND<>'Y' AND EXT_CPY_STAT<>'D'
AND EVENT_TS>=<Parameters.Start Date> ORDER BY EVENT_TS
Also, I am doing this in Tableau's Custom SQL Query feature... which.. without knowing anything about SQL or the basic syntax... seems to not like any fancy tricks. Maybe it does... I don't know... But all I've gotten are errors using other people's scripts. It seems very specific on the syntax it wants to see.

Answer 1

Assuming that every other field you're selecting on (besides the date) is also duplicated, you can use some aggregation in your query to squish the output records together, using either the min(event_ts) or max(event_ts) depending on what you want to see:
SELECT MIN(EVENT_TS) as EVENT_TS
,EVENT_NO
,FAC_PROD_FAM_CD
,SER_NO
,DISC_AREA_ID
,DISC_AREA_DESC
,QUALITY_VELOCITY
,CMPNT_SERIAL_NO
,PROTOTYPE_IND
,EXT_CPY_STAT
FROM ABUS_DW.V_BIQ_R8_QWB_EVENTS
WHERE FAC_PROD_FAM_CD IN ('ACOM', 'SCOM', 'LAP', 'RM', 'SCRD')
AND DISC_AREA_ID IN ('400','450')
AND PROTOTYPE_IND <> 'Y'
AND EXT_CPY_STAT <> 'D'
AND EVENT_TS >= <Parameters.Start DATE>
GROUP BY
EVENT_NO
,FAC_PROD_FAM_CD
,SER_NO
,DISC_AREA_ID
,DISC_AREA_DESC
,QUALITY_VELOCITY
,CMPNT_SERIAL_NO
,PROTOTYPE_IND
,EXT_CPY_STAT
ORDER BY EVENT_TS
If each row of your duplicate records has distinct values for FAC_PROD_FAM_CD, SER_NO, DISC_AREA_ID, etc... then you'll have to get fancier. You could use a correlated subquery as one option:
SELECT EVENT_TS
,EVENT_NO
,FAC_PROD_FAM_CD
,SER_NO
,DISC_AREA_ID
,DISC_AREA_DESC
,QUALITY_VELOCITY
,CMPNT_SERIAL_NO
,PROTOTYPE_IND
,EXT_CPY_STAT
FROM ABUS_DW.V_BIQ_R8_QWB_EVENTS AS t1
WHERE FAC_PROD_FAM_CD IN ('ACOM', 'SCOM', 'LAP', 'RM', 'SCRD')
AND DISC_AREA_ID IN ('400','450')
AND PROTOTYPE_IND <> 'Y'
AND EXT_CPY_STAT <> 'D'
AND EVENT_TS =
(
SELECT MIN(EVENT_TS)
FROM ABUS_DW.V_BIQ_R8_QWB_EVENTS
WHERE FAC_PROD_FAM_CD IN ('ACOM', 'SCOM', 'LAP', 'RM', 'SCRD')
AND DISC_AREA_ID IN ('400','450')
AND PROTOTYPE_IND <> 'Y'
AND EXT_CPY_STAT <> 'D'
AND EVENT_TS >= <Parameters.Start DATE>
AND t1.EVENT_ID = EVENT_ID
)
ORDER BY EVENT_TS;
Here, in a subquery, we get the min(event_ts) for the event_id given all the same WHERE conditions and then we restrict the main query by that min(event_id).