Double insert in one INSERT..SELECT query

For example, I have the following code:

INSERT INTO table_prices(price, comment)
    SELECT a.price, 'first'
    FROM first_price AS a
UNION
    SELECT a.price, 'second'
    FROM second_price AS a;

And i have a result in table "table_prices":

id                      price                   comment
1                       first_price1            first
2                       first_price2            first
3                       first_price3            first
...                     ...                     ...
15                      second_price1           second
16                      second_price2           second
...                     ...                     ...

But I need the following:

id                      price                   comment
1                       first_price1            first
2                   开发者_开发问答    second_price1           second
3                       first_price2            first
4                       second_price2           second
...                     ...                     ...

Could you help me - how can I achieve this? TIA!

---

you can use ORDER BY

ORDER BY id

---

Ordering rows in union selects requires temporary table, something like this should work:

INSERT INTO table_prices(price, comment)
SELECT `price`,`comment`
FROM (
        SELECT a.price AS `price`, 'first' as `comment`
        FROM first_price AS a
        UNION
        SELECT a.price, 'second'
        FROM second_price AS a
    ) temp_table
ORDER BY `price`