Hi so i have table called products, i have some information there like name,netto price,tax etc. I want to add new records named brutto\_price which is automatically calculated as (netto\_price + netto\_price\*tax) or (netto\_price \*1.22 if tax is null) its not allowed to insert null into netto\_price. (tax could be null).
Im doing sth like this 

```
alter table products add (brutto_price FLOAT DEFAULT netto_price*1.22 )

    UPDATE products
   SET brutto_price = netto_price + netto_price*tax
   where
   tax is not null;

```

but first query is not working (probably because i use record name in this) any idea?
['https://Stackoverflow.com/questions/61850588', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/13560269/']
You can use 

```
{(book.authors || []).map(({firstname, lastname}) => `${lastname} ${firstname}`).join(", ")}. 

```

This will give you comma separated names

```
<tbody>
{books.length === 0 ?
    <tr align="center">
        <td colSpan="6">{this.state.books.length} List is empty.</td>
    </tr> :
    books.map((book) => (
        <tr key={book.id}>
            <td>{book.id}</td>
            <td>{book.title}</td>
            <td>{(book.authors || []).map(({firstname, lastname}) => `${lastname} ${firstname}`)}</td>
            <td>{book.description}</td>
            <td>{book.language}</td>
            <td>{book.price}</td>
            <td>{book.action}</td>
        </tr>
    ))
}
</tbody>

```
One of the ways to do that:

```

(book.authors || []).map(author => author.firstname + ' ' + author.lastname).join(', ')

```