Repeat the previous question for SQL, the database query language (for an introduction, type “SQL tutorial” into your favorite Internet search engine). Spreadsheets like Microsoft Excel are sometimes...

Repeat the previous question for SQL, the database query language (for an introduction, type “SQL tutorial” into your favorite Internet search engine). Spreadsheets like Microsoft Excel are sometimes characterized as declarative programming. Is this fair? Ignoring extensions like Visual Basic macros, does the ability to define relationships among cells provide Turing complete expressive power? Compare the execution model to that of Prolog. How is the order of update for cells determined? Can data be pushed “both ways,” as they can in Prolog?