Question

I have a table where I can have multiple names for a given id like this:

a_table (id int, name varchar(100), priority int);

I need a query that will search on names but make sure it will return only 1 name for each id, and that name will be the one with the higher priority.

e.g. if my data are

1, AaaB, 2
1, AbbB, 1
1, AccB, 0
2, foo, 0
3, AddC, 0

I want my query for "A%" to return:

1, AaaB
3, AddC

I was thinking something like:

select * from a_table where name like 'A%' group by id;

But this will not guarantee that the value with the higher priority will be selected.

Any ideas?

Answer 1

I believe you want what the MySQL documentation calls the rows holding the group-wise maximum of a certain column:

For the task "For each article, find the dealer or dealers with the most expensive price":

SELECT article, dealer, price
FROM   shop s1
WHERE  price=(SELECT MAX(s2.price)
             FROM shop s2
             WHERE s1.article = s2.article)
ORDER BY article;

+---------+--------+-------+
| article | dealer | price |
+---------+--------+-------+
|    0001 | B      |  3.99 |
|    0002 | A      | 10.99 |
|    0003 | C      |  1.69 |
|    0004 | D      | 19.95 |
+---------+--------+-------+