Difference between orcle, DB2 and Mysql?

Question

What is exact difference between these three DBMS? What are their features? Wch is best?

Answer 1

While it may be difficult to find unbiased comparisons, this one is probably quite realistic
https://db-engines.com/en/system/IBM+Db2%3BMySQL%3BOracle

Db2 is owned by IBM and it is a niche product, rather focused on analytics and the merging of OLTP and OLAP capabilities.

Oracle is the undisputed de facto leader in enterprise database solutions. The Oracle DB is so good that even its big rival in ERP applications, SAP uses Oracle databases. They offer database also as cloud service, run on specially engineered hardware.

Oracle also purchased MySQL recently. This is still an open source product so suitable for smaller projects but Oracle is injecting a lot of goodies in it like NOSQL support. #1 fav of open source developers.