Select statement can have multiple table #2

[ivanceras]

No description provided.

[Imran-imtiaz48]

The first! macro in Rust is a concise and effective utility designed to safely retrieve the first element from a collection. It provides two overloads: one for general expressions with a custom name for clearer error messaging, and another shorthand for accessing a specific field of a struct. When the target array or vector has at least one element, the macro returns a reference to the first item. Otherwise, it invokes a custom raise! macro to produce a descriptive runtime error, improving debugging and ensuring program safety. Its use of stringify! and concat! macros to craft meaningful error messages makes it particularly useful in validating required input data during runtime. Overall, this macro enhances code readability and robustness by abstracting a common pattern of safe array access with expressive error handling.