SQL Server - Queries, Views or Stored Procedures run slow after upgrade

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http://thomaslarock.com/2014/06/upgrading-to-sql-server-2014-a-dozen-things-to-check/

DBCC CHECKDB WITH DATA_PURITY;

DBCC UPDATEUSAGE(db_name);
EXEC sp_MSforeachtable @command1='UPDATE STATISTICS ? WITH FULLSCAN';