**Use case**
`SELECT POSITION('/' IN s) FROM (SELECT 'Hello/World' AS s);`

The same as `position(s, '/')`

if (pos->type == TokenType::QuotedIdentifier)
    {
        ReadBufferFromMemory buf(pos->begin, pos->size());
        String s;
        if (*pos->begin == '`')
            readBackQuotedStringWithSQLStyle(s, buf);
        else
            readDoubleQuotedStringWithSQLStyle(s, buf);
        if (s.empty())    
            return false;
        node = std::make_shared<ASTIdentifier>(s);
        ++pos;
        return true;
    }
    else if (pos->type == TokenType::BareWord)
    {
        node = std::make_shared<ASTIdentifier>(String(pos->begin, pos->end));
        ++pos;
        return true;
    }
    else if (allow_query_parameter && pos->type == TokenType::OpeningCurlyBrace)
    {
        ++pos;
        if (pos->type != TokenType::BareWord)
        {
            expected.add(pos, "substitution name (identifier)");
            return false;
        }
        String name(pos->begin, pos->end);
        ++pos;