TOP relational databases are MS-SQL , Oracle and others.
MS-SQL server has very compatible with normal companies to do their Billing System, Customer care , Data management .
Oracle Database is much complicated than MS-SQL , but usually better to use big companies who has TB Data-s. Review collected by and hosted on G2.com.
I will say migration Data-s to new Versions usually takes lots of time and knowledge. Review collected by and hosted on G2.com.

