Lem-E-Tweakit and Logic programming

While watching the SICP lectures 8a & 8b, one thing that i realized is that this logic programming they mention seems to be very similar to kind of things we use SQL for, just better… ie. a lot more flexible.

So why we do use SQL after all?

After a bit of googling found this good article: http://search.cpan.org/dist /AI-Prolog/lib/AI/Prolog/Article.pod one of the references says:

“…So if Prolog(read AI) and SQL(DB) are so similar, Why is one so successful commercially and the other deemed a complete failure in terms of scalability?…”

Relational Databases implement powerful techniques to improve performance:

• Indexing
• Hashing
• Reordering goals to reduce backtracking

Where as Prolog based systems have very few such techniques.

What is SQL missing?

One of the most powerful features of Prolog is recursion.

SQL does not have recursion built into it. This is a severe Handicap. However there is a way to overcome this problem by invoking multiple SQL queries from a host language like C Or Java. SQL3 has begun supporting recursion.