>>>> (Anybody have any clue how the relational calculus is different from 
>>>> the relational algebra??)
>>>
>>> Yes.
>>
>> Care to explain?
> 
> It's kind of like the difference between functional and procedural.
> 
> In the calculus, you say "give me a table with the name, salary, and 
> hire date from table X and table Y where X.name=Y.name and salary < 500"
> 
> In the algebra, you say "join table X and Y, and from that select the 
> ones where the names are the same, and from that select the ones where 
> the salary is < 500, and from that project over name, salary, and hire."
> 
> Think of SQL compared to something like
> 
> (((X join Y) select {salary < 500})
>     select {X.name = Y.name}) project [name,salary,hire]
> 
> Only select, project, and join are defined in the algebra. There's no 
> "exists" and such.

So are the two formalisms of equivilent expressive power?

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