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

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

}
    else
    {
        auto function_node = std::make_shared<ASTFunction>();
        function_node->name = "tuple";
        function_node->arguments = contents_node;
        function_node->children.push_back(contents_node);
        node = function_node;
    }
    return true;
}
bool ParserSubquery::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{
    ASTPtr select_node;
    ParserSelectWithUnionQuery select;
    if (pos->type != TokenType::OpeningRoundBracket)
        return false;
    ++pos;
    if (!select.parse(pos, select_node, expected))
        return false;
    if (pos->type != TokenType::ClosingRoundBracket)
        return false;
    ++pos;
    node = std::make_shared<ASTSubquery>();
    node->children.push_back(select_node);
    return true;
}
bool ParserIdentifier::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{