MySQL Cookbook

Problem

Has any database been selected as the default database? What is its name?

Solution

Use the DATABASE⁠(⁠ ⁠ ⁠) function.

Discussion

SELECT DATABASE⁠(⁠ ⁠ ⁠) returns the name of the default database or NULL if no database has been selected. The following Ruby code uses the statement to present a status display containing information about the current connection:

db = dbh.select_one("SELECT DATABASE()")[0] puts "Default database: " + (db.nil? ? "(no database selected)" : db)

Note that before MySQL 4.1.1, DATABASE⁠(⁠ ⁠ ⁠) returns an empty string (not NULL) if there is no current database.