The impact of SQL injection attacks may vary from congregation of sensitive data to manipulating database information, and from executing system-level commands to denial of service of the application.
Types of SQL Injection:
1.In-band SQLi (Classic SQLi)
4.Inferential SQLi (Blind SQLi)
5.Boolean-based (content-based) Blind SQLi
6.Time-based Blind SQLi
For more information click: