Multiversion Concurrency Control
Every developer I know of has used or uses databases on a daily basis, be it SQL Server or Oracle but quite a few of them are stumped when asked how this SQL will execute and what would its output be. insert into Employee select * from Employee; Select * from Employee; Additionally what happens if multiple people execute this statement concurrently. Will the select lock the insert ? Will the insert lock the select ? How does the system maintain data integrity in this case ? The answers have ranged from, this is not a valid SQL statement to this will be an indefinite loop. ...