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https://knowledge-base.havit.cz/2014/05/10/sql-2014-localdb-instance-v12-0-neni-automaticky-zalozena-50-local-database-runtime-error-occurred-the-specified-localdb-instance-does-not-exist/
SQL 2014 LocalDB: Instance “v12.0” není automaticky založena (50 - Local Database Runtime error occurred. The specified LocalDB instance does not exist.)