User defined functions[1] in MySQL are dynamic libraries which are loaded and then you attach a function name to. A common example might be a hashing function

User defined functions[1] in MySQL are dynamic libraries which are loaded and then you attach a function name to. A common example might be a hashing function that you want the DB to understand.[2] That said, I bet just about every database supports something similar (and postgres' equivalent has already been provided by a sibling comment). 1: https://dev.mysql.com/doc/refman/5.5/en/create-function-udf.html https://dev.mysql.com/doc/refman/5.5/en/create-function-udf.... 2: https://www.percona.com/doc/percona-server/LATEST/management/udf_percona_toolkit.html https://www.percona.com/doc/percona-server/LATEST/management...