Prefix matching is both very common and important in telephony applications,
where call routing and costs depend on matching caller/callee phone number
to an operator prefix.

Let's say the prefixes table is called prefixes, a typical query will try to
match a phone number to the longest prefix in the table:

SELECT *
  FROM prefixes
 WHERE prefix @> '0123456789'
ORDER BY length(prefix) DESC LIMIT 1;