What are some of the major limitations of using SQL 2012 Express with SharePoint server 2013, is there any Sharepoint 2013's functionnality or service that doesn't running in using Sql Express and what is availaible in using SQL server 2012 ?
There are several limitations that affect the SharePoint Server 2013 running under SQL Server 2012 express:
- You have only one cpu (with 4 cores) available for the sql server
- You can only assign 1 GB Ram for the sql server express instance
- You have only 10GB per database
- It will be harder to scale out your farm later on
- The User Profile Sync won't work
Especially in search projects you will hit the limits very early.
You can find a comparison of the sql server editions here: http://www.microsoft.com/en-us/server-cloud/products/sql-server-editions/overview.aspx#fbid=qsN72_bpfsk
The rest of the functionalities of SharePoint 2013 are working. For a test environment or quick developments it's OK, but it's not fun.