Implement three SQL queries (try_lock, check_lock, release_lock) to support a recursive record locking mechanism on a table whose elements are arranged in a tree, using the locked_at / locked_by pattern. Have a look at the small specification document for more details.
## Deliverables
1) All deliverables will be considered "work made for hire" under U.S. Copyright law. Employer will receive exclusive and complete copyrights to all work purchased. (No 3rd party components unless all copyright ramifications are explained AND AGREED TO by the employer on the site per the worker's Worker Legal Agreement).
## Platform
Use you preferred database chosen among: sqlite3, mysql, postgresql, Microsoft Access 2000-2003, MSSQL 2005-2008, Oracle 10. Use standard, portable SQL.