how to select record fields that start with capital?

[wowJasonCorderoy]

Hi,
It's too late now to change table column names. How do I query column names that begin with capital letter from Logica?

When I do something similar to:

Sets(colA:, ColB:) distinct:- 
`project.dataset.table`(colA:, ColB:)

I get this error:
Record fields may not start with capital letter, as it is reserved for predicate literals.
Backtick the field name if you need it capitalized. E.g. "Q(A: 1)".

colA is fine but ColB produces an error.
If I just do this instead then no error:

Sets(colA:) distinct:- 
`project.dataset.table`(colA:)

I tried adding backticks around ColB, didn't work.
What do I need to do to query fields that start with capital letter?

Thanks

[EvgSkv]

Hello,
if your table has uppercase-named columns then we need to store the value of the column in an intermediate variable like so

@Engine("sqlite");
@With(T);
T(colA: "value A", ColB: "value B");
Q(colA: x, ColB: y) :- T(colA: x, ColB: y);

Let me know if you have further questions!

[wowJasonCorderoy]

Great thank you.
Worked once I used your suggestion but changed my code to:

%%logica Q
Q(colA:x, ColB:y) distinct:- 
`project.dataset.table`(colA:x, ColB:y);

But it still returns colA and ColB as column names. That's really cool.
Thanks you.
I am new to this language and struggle with some basic things so really appreciate you taking the time to help me out.

[wowJasonCorderoy]

Sorry to keep hassling you but...
At the moment I'm trying to convert logica code to basic human sentences.

So using your code:

@With(T);
T(colA: "value A", ColB: "value B");
Q(colA: x, ColB: y) :- T(colA: x, ColB: y);

Am I correct in thinking of it like:
With predicate T, Where T is a table
containing columns colA and ColB, with values "value A" and "value B" respectively,
Predicate Q (in this case a table) is the result of querying table T's colA and colB, with colA and ColB stored as intermediate variables x and y respectively.

I'm new to logical programming.
Is my above way of thinking correct or am I making life difficult for myself thinking in this way?
Feel free to recommend any books. It's just I found a very basic understanding of prolog didn't help me all that much in reading through logica code. But am really keen to improve at logica.

Thanks

[EvgSkv]

Hello @wowJasonCorderoy !
no worries, bring all you questions here 😄

Yes, your interpretation of the code is correct.

And for real-world inspired programs Logica converts to natural sentences even better.
Consider this example:

Parent("Queen Victoria", "King Edward VII");
Parent("Queen Victoria", "Prince Leopold");
Parent("King Edward VII", "King George V");
Parent("King Edward VII", "Maud of Wales");
Parent("King George V", "King George VI");
Parent("King George VI", "Queen Elizabeth II");
Parent("Queen Elizabeth II", "Prince Charles");
Parent("Queen Victoria", "Prince Arthur");
Parent("Prince Arthur", "Margaret Princess of Sweden");
Parent("Margaret Princess of Sweden",
       "Ingrid Queen of Denmark");
Parent("Margaret Princess of Sweden",
       "Prince Gustaf Adolf");

Grandparent(a, c) :- Parent(a, b), Parent(b, c);

We would convert it to natural sentences line by line as:

• Queen Victoria is a parent of King Edward VII,
• Queen Victoria is a parent of Prince Leopold,
  [etc]

And finally:
"a is grandparent of c if and only if there exists b such that a is a parent of b and b is a parent of c."

Logic programming is designed to match how we think of data intuitively.

I am not up-to-date with what are best books for studying logic programming nowadays, maybe someone else can comment on this. You've probably seen Logica Tutorial, let me know if you have any questions on going over it.

Cheers!