MySQL is a free and open source relational database. It is stable and reliable enough to be adopted by many high traffic and popular websites. Over a period of time it has overcome several limitations and now provides many features expected of modern database systems like support for very large rows and tables, table partitioning, document store, GIS storage of data etc.
The community and the product has gained immensely after its acquisition by Oracle. Oracle has added focus on speed, reliability and scalability and developed several tools and extensions which can support larger enterprise use cases. Many of them are however paid for.
MySQL workbench provides a suite of powerful tools to manage the server as well as for designing the database. It has a database designer as well as reverse engineering tools, profiler, query planner and many more.
Its ease of use, availability across platforms and free license has contributed immensely to its popularity and is the defecto database in most open source software. Mysql will serve well for most of the projects.
MS Sql is a popular database engine available from microsoft. It has a free to use but limited by license version going by name of express which can serve a fair sized application very well. Being a microsoft product it integrates well with windows in both desktop and server environments.
Its full featured version comes with additional tools like reporting services, analytics services, integration services. Scale and Volume have been designed into it with possibility of deployment as clusters.
Microsoft has developed several proprietary extensions like ranking, grouping and ordering functions, Common Table Expression to make simplify developer tasks and sometimes increase the speed of execution
It provides enterprise security with integration with active directory or ldap servers, encrypted records, automated audit logs.
MS SQL comes with MS SQL Management Studio which is an all in one GUI based tool to manage and develop. Visual studio also offers deeper integration and provides additional tools which can help develop applications using MS SQL faster. It provides capabilities to create databases from model and vice versa.
MS SQL comes with complex licensing terms and a very steep licensing fee. This however has become less of a problem in the era of cloud computing.
MS SQL is a right solution for businesses which seek the safety and reliability of having a vendor backed support, quick and reliable patch and fixes cycle, homogenous environment and ecosystem. Microsoft partner program also gives access to verified and reliable vendors for MS SQL based solutions.
Relational databases have been the norm as far as data storage is concerned. However, they can be slower due to the reliability that they promise. With the increase of unstructured data in form of text, document, images etc, that reliability was coming at a high cost of speed which the cloud scale applications needed.
No-SQL databases evolved out of a need for high throughput systems which can allow updates to its underlying structures on the fly and still provide a fair amount of reliability.
MongoDB is a popular open source No-SQL database designed for speed and scalability. It connects asynchronously over HTTP and uses documents as its unit of storage. It can partition data horizontally as well as vertically. It can be deployed over a cluster transparently to the external systems. It comes with inbuilt services to manage data availability, distribution, collation of query results and some load distribution. While it is a No-SQL database, it still has support and reliability of ACID transactions.