Re: two simple questions

gbiltz wrote:
>
> Could someone please be kind enough to explain the difference between PL/SQL
> and SQL PLUS ? And also the definition of " := " ?

Others have answered the first part adequately and have commented on the second. I'd like to fill in some gaps with the second part.

PL/SQL is a 3GL language that is based on a blocked structure as opposed to a function-based structure or a sequential structure.

Fortran and Cobol are both sequential structures and while they both have the abililty to have sub-programs that are equivalent to procedures and functions, they are not natively conducive to structured programming. RPG II/III is similar in a way except that i/o is handled very differently. In this class of language there is no standard for either assignment or equality operators - some are verbose while others are terse.

The main function-based language that most programmers know is C/C++, but VB can also be considered in the same class because each procedure and function is sequential within its own scope. In this class of language the assignment operator is '=' and there is no standard for the equality operator (in C it is '==' while in VB it is '='). In general, nawk and perl also fit in this class.

The third class of programs is block-based programs. The first of these that I know of was either PL/I or Pascal (not sure which one really came first) More recently this group of langauges has included ADA, Modula II/III, Rexx and now PL/SQL. The main distinguishing characteristic of block-based languages is that they allow nested procedures/functions. That is to say, within any given procedure or function you can also define other procedures and functions. In this class of language the assignment operator is ':=' while the equality operator is simply '='. Just as a side-note, all of the languages in this class were ultimately influenced by a dude named Niklaus Wirth (know as "Uncle Nicky" to many who have been around a long time) who wrote a book entitled "Algorithms + Data Structures = Programs" - a book that you either get or don't get. If you "get" it, your view of programming will be changed forever and you'll be a better programmer. If you don't "get" it you will be in the majority of individuals who program today and don't understand beans about structured programming and algorithmic approaches to solving programming problems.

I realize that not all high level languages that have ever been used would fit into one of these categories. Languages like Lisp, Prolog and Nomad seem to defy any classification. Received on Wed Jan 10 2001 - 07:42:21 CST