Microsoft Azure SQL Database is a managed cloud database provided as part of Microsoft Azure.
Db2 is a family of data management products, including database servers, developed by IBM. They initially supported the relational model, but were extended to support object–relational features and non-relational structures like JSON and XML.
Amazon Redshift is a data center product that is part of the broader Amazon Web Services cloud-computing network. The name implies moving away from Oracle, with red being an allusion to Oracle, whose corporate color is red and known informally as "Big Red."
BigQuery is a fully-managed, serverless data warehouse that enables scalable analysis over petabytes of data. It is a Platform as a Service that supports querying using ANSI SQL. It also has built-in machine learning capabilities. BigQuery was announced in May 2010 and made generally available in November 2011.
Amazon Aurora is a relational database service developed and offered by Amazon Web Services beginning in October 2014. Aurora is available as part of the Amazon Relational Database Service.