Pros:
- it is convenient to type and read numbers this way;
- Ada, Perl, C++, Go and Rust already support that;
- can support thousands as well as lakhs and crores;

Cons:
- standard SQL does not have this support;
- PostgreSQL treat `SELECT 1_000_000` as number one with `_000_000` alias: http://sqlfiddle.com/#!17/0a28f/400
- C++ has `1'000'000` instead of `1_000_000`;

What do you think?

{
    ASTPtr collation;
    if (!ParserIdentifier(true).parse(pos, collation, expected))
        return false;
    
    const String name = getIdentifierName(collation);
    bool valid_collation = name == "binary" ||
                           endsWith(name, "_bin") ||
                           endsWith(name, "_ci") ||
                           endsWith(name, "_cs") ||
                           endsWith(name, "_ks");
    if (!valid_collation)
        return false;
    auto collation_node = std::make_shared<ASTCollation>();
    collation_node->collation = collation;
    node = collation_node;
    return true;
}
template <TokenType ...tokens>
static bool isOneOf(TokenType token)