Answer 1

(Not an SQL expert) But I think the arguments could only be 2 and not 3.

Answer 2

IMHO the problem is not with the lesson, the problem is, each major DBMS vendor has their own ideas about what is best for their product users. And they all believe their design and/or policy is the best there is.

Due to the differences, it is quite common for one SQL learner to encounter an issue with syntax difference incompatibility amongst major DBMS vendors, like what we have here today, with the CONCAT function.

MySQL and MSSQL agreed to use similar syntax for CONCAT function, the function accepts multiple arguments and will produce a new string by concatenating each arguments. But Oracle's choose to agree that CONCAT function should ONLY accept two arguments, which explains the error message you got.

The lesson, as it seems to me, was built on the assumption that learners will be using MySQL (or something compatible). Thus, we can't really say the examples are outdated or inaccurate. This is more of a problem in relation to syntax differences amongst DBMS products : )

Answer 3

STANDARD DEVIATION X2 - Sno Erika
TBH, I am also a bit bothered by the differences, but what can I say, the DBMS vendors are giant companies, and I was just another product user : )

I don't know if incorporation of all the syntax differences was possible, there are loads of them. Funnily, some issues also differ by product version.

I can imagine how time consuming it would be trying to compile all the syntax differences or incompatibilities and list them in the lesson; only to find that the next release of a certain product renders the lesson materials invalid, yet again XD