For a MySQL database export:
mysqldump -u username -p database_name > /tmp/dump.sql
^^ from the *nix command line
For a particular table in a database
mysqldump -u username -p database_name table_name > /tmp/dump.sql
^^ also from the *nix command line
You will then be prompted for the password for the specified user, shortly thereafter, you’ll have your db export (or as some folks like to call it, a “db dump” — gah! Hate that name… gross!)
Tired of always typing in your username/password when using mysql via the CLI? Check out how to set up a .my.cnf!