MS SQL Express is a free distribution of MS SQL server. It means that there are certain limits of its usage described in the table below.
| Limitation | MSSQL 2005/2008 Express | MSSQL 2008R2 Express | MSSQL 2012 Express | MSSQL 2014 Express | MSSQL 2016 Express |
| The number of simultaneous connections | no limit | no limit | no limit | no limit | no limit |
| Max. database size | 4 GB | 10 GB | 10 GB | 10 GB | 10 GB |
| Max. RAM usage | 1 GB | 1 GB | 1 GB | 1 GB | 1410 MB |
| The number of used processors | 1 | 1 | 1 | 1CPU / 4 core | 1CPU / 4 core |