Which sql language MySql,SQLServer,etc is widely used in data science?
Generally in data science, the techniques you use matter more than the tools. This is because, even if you rely on a “not so sophisticated” tool, knowledge of techniques can make or break your product
Usually - it would depend on company to company. If you are working in a web / technology company, you can expect a MySQL or Postgre. If you are in a corporate, which had a SQL server before hand - they might continue to use the same.
As Faizan mentioned, as long as you are comortable with one of the SQL to extract data and run queries on it, you are in good place.