Before you Upgrade to SQL 2012 where SharePoint databases reside.
Please make sure to go through these articles before you upgrade to SQL 2012 where SharePoint databases are hosted.
SQL server 2012 is supported and works with SharePoint 2010 only if the SharePoint environment is on SP1 or higher
https://msdn.microsoft.com/en-us/library/hh231665(v=sql.110).aspx
Upgrade to SQL Server 2012
https://msdn.microsoft.com/en-us/library/bb677622.aspx
Supported Version and Edition Upgrades
https://msdn.microsoft.com/en-us/library/ms143393.aspx
Upgrade PowerPivot for SharePoint
https://msdn.microsoft.com/en-us/library/ee210646(SQL.110).aspx
Upgrade and Migrate Reporting Services
https://msdn.microsoft.com/en-us/library/ms143747.aspx
Upgrade Analysis Services