Question

I am taking the free Stanford database course online. I don’t have any DB experience, but have many years of OS programming experience. Typically, I will flowchart or write out pseudo-code for a particular algorithm before coding it up. I was wondering if this technique can be used to go from a flowchart or pseudo-code into SQL statements.

Does a loop that iterates over a set match a WHERE clause? Is this mostly(?) or always(?) true?

How would you map a doubly nested loop into SQL?

Answer 1

SQL uses set-based logic (relational algebra/calculus), whereas most programming languages are imperative/procedural (e.g. C#, Java, etc).

If you write set-based logic pseudocode then it should be just as straightforward to translate to SQL as imperative pseudo-code is to translate to C#.

An example of set-based logic pseudo code might be something like this:

1.Join book stores and titles over the BookstoreID.
2.Restrict the result of that join to tuples for the book Some Sample Book.
3.Project the result of that restriction over StoreName and StorePhone.

If you are trying to convert imperative pseudo-code to SQL (or set-based pseudo-code to C#) it’s going to be much more painful.