Question

I got the following mysql table

PrefixID + Prefix
001      + 110
005      + 550
005      + 550
005      + 550
005      + 550

and I want to turn it into the following table

PrefixID + Prefix + Count
001      + 110    + 1
005      + 550    + 4

Count is just the frequency of that particular prefix
How can i achieved that?

Answer 1

Use a GROUP BY clause and a COUNT() aggregate:

SELECT `PrefixID`
     , `Prefix`
     , COUNT(1) AS `Count`
  FROM mytable
 GROUP BY `PrefixID`, `Prefix`

From your sample data, it appears that the Prefix and PrefixID are dependent (one to one correspondence.) You may need to adjust the query, depending if you want to guarantee that either PrefixID or Prefix is unique in the resultset.