Here is a list of free good database management software:
Oracle SQL Developer (manage Oracle db and also MySQL, SQL Server and Access)
phpMyAdmin (MySQL administration tool written in PHP, so you can use it via web server)
phpMSAdmin (as above but for MS SQL Server database)
SQL Server Web Data Administrator (as above but by Microsoft)
SQLyog Community Edition (MySQL database management)
DBeaver written in Java, 100% free and light, supports many databases