I am having copy of content database from client. Now i need to find permission level for particular user using SQL query. Is it possible?
First of all never query content database. You will end up violating your license.
Restore the content database and attach it to a web application.
Use Powershell or Visual Studio to write a small piece of code to query the SPSite object against the user who permissions needs to be identified.
I would recommend to go for this simple powershell script available in codeplex that will suffice for the requirement you mentioned.