What kind of SQL notation is using LibreOffice Base?

I’m starting to use functions typing SQL code in LibreOffice Base… however I see differences between the SQL code suggested by several websites and LibreOffice Base…

For example, at w3schools.com they would suggest me this code to introduce the current system date and hour into a field of my database (sorry for the fields are in Spanish)…

SELECT
ID_Empleados,
Nombre,
Apellido1ero,
Direccion,

NOW( )
PerDate

FROM
tbl_EMPLEADOS

Okay, that code will fail in LibreOffice Base, and it is SQL …

???

However, if I use " " then the code work…

This code will work in LibreOffice Base…

SELECT
“ID_Empleados”,
“Nombre”,
“Apellido1ero”,
“Direccion”,

NOW( )
“PerDate”

FROM
“tbl_EMPLEADOS”

So I really don’t know why do we have those differences and if LibreOffice Base is using a kind SQL following a certain standard or specification…
I find differences between the SQL code from w3schools.com and the SQL code implemented by LibreOffice Base

I’d like to find a website where may I see SQL functions with examples of code that works fine in LibreOffice Base, however that web site, offer me SQL code but … don’t work in LibreOffice Base due minor differences in the code notation, etc.

So what kind of SQL is using LibreOffice Base?

Could we tell me any website where may I consult the whole SQL functions, etc. but with code examples that work fine in LibreOffice Base?

Cheers

Wikipedia article for LO would had told. You didn’t even try to look, at least not there. Wikipedia is first place I look in.

Java-based HSQLDB (HyperSQL DataBase). I read from here v1.8 is used, which, oddly, isn’t mentioned anywhere as far as I see.

The documentation about HSQLDB is here:
http://hsqldb.org/doc/2.0/guide/guide.pdf

However this guide it’s complicated and although I see a big description of every command, I don’t see code examples easy to understand in the fashion of w3schools.com

Would you know any website describing examples of code with HSQLDB for LibreOffice Base?