Unless you can implement Snort-Inline it does only "scan" - But, it Alerts you and logs too
Well, first of all, please accept my apologies. English is my second language, and I didn't explain myself correctly.
I should have said 'I thought that SNORT scans only network traffic'. I didn't know it has the ability to scan SQL Server's activities. All I want is an IDS, and for what I have seen SNORT does that job quite well.
I stopped considering SNORT on the false knowledge that it didn't checked SQL Server's activities.
Now that you showed me that it does detect intrusion on the sql servers, I will do some research and try to implement it.

Once again, thank you

Cheers!