Planet NoSQL

  Learning SQL is easy; Implementing SQL, not so much. Halloween has come and gone. But, the tricks of the Halloween problem is here to stay! This has to be solved by databases every day. SQL made the relational database easy, accessible, and successful. SQL may be easy to write, but its implementation hides a lot of complexity. From the days of  System R  to NoSQL systems, all of us implementing SQL and SQL inspired languages like  N1QL , have to learn the rules, requirements to ensure the declarative query language continues its  extraordinary effectiveness and correctness.  One such problem is  the Halloween Problem . I'll describe the problem briefly here. I highly recommend reading its  history  in the IEEE Annals of the history of computing - second link in the references section below. The Problem: Consider a simple table and index: Java 1 CREATE TABLE t ( empid int primary key , salary int ); 2 CREATE INDEX i1 ON t ( salary...