Deleting duplicates from a large table

Question

I have quite a large table with 19 000 000 records, and I have problem with duplicate rows. There\'s a lot of similar questions even here in SO, but none of them seems to gi

Answer 1

UPDATE table SET datetime  = null 
WHERE location_id IN (
SELECT location_id 
FROM table as tableBis
WHERE tableBis.location_id = table.location_id
AND table.datetime > tableBis.datetime)

SELECT * INTO tableCopyWithNoDuplicate FROM table WHERE datetime is not null

DROp TABLE table 

RENAME tableCopyWithNoDuplicate to table

So you keep the line with the lower datetime. I'm not sure about perf, it depends on your table column, your server etc...