Name 5 Relational Database Management Systems that are the most popular?

Name 5 Relational Database Management Systems that are the most popular and also tell me which Query Language is used the most...is it SQL?if it is....which derivative of SQL is used the most T-SQL or PL/SQL.and yes what percent of Relational Database Management Systems use SQL as their standard Query Language.If... show more Name 5 Relational Database Management Systems that are the most popular and also tell me which Query Language is used the most...is it SQL?if it is....which derivative of SQL is used the most T-SQL or PL/SQL.and yes what percent of Relational Database Management Systems use SQL as their standard Query Language.If you can point to additional sources regarding this,it would be quite helpful as well.Waiting eagerly for your answers.
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