Question

I have a mysql table. The headers are structured like so:

field   field   field   field   vendors
data   data    data    data    data
data   data    data    data    data
data   data    data    data    data2
data   data    data    data    data2
data   data    data    data    data2

Now, I want remove duplicate rows of rows sharing the same vendor value. So two rows that are the same but have different vendor column value should not be considered duplicate. But, two or more rows that equal and share the same vendor value would be considered duplicates and should be removed, leaving only one existing copy.

How can this be done using mysql?

I did something like this but it deletes everything instead of just the duplicate values. I want at least one copy remaining.

DELETE

FROM auto
WHERE ((auto.email=’[e-mail]’) AND (auto.vendors=’5552′))

Answer 1

"DELETE x
 FROM $table x
 LEFT
 JOIN
 ( SELECT vendors
        , email
        , MIN(lead_id) min_lead_id
     FROM $table
    GROUP
       BY vendors
        , email
 ) y
ON y.vendors = x.vendors
AND y.email = x.email
AND y.min_lead_id = x.lead_id
WHERE x.vendors = $vendor
AND y.min_lead_id IS NULL;";

This will do it. Simply replace the php variables in that code with the correct values.

$vendor = name of vendor column
$table = name of table

The only problem with this code is that its not fully optimal. With a 25,000 record set and running in a virtual dedicated server it completes the task at an average of 2 minutes.

Cheers