How to get all the fields of a row using the SQL MAX function?
Consider this table (from http://www.tizag.com/mysqlTutorial/mysqlmax.php):
Id name type price
123451 Park's Great Hits Music 19.99
123452 Silly Puddy Toy 3.99
123453 Playstation Toy 89.95
123454 Men's T-Shirt Clothing 32.50
123455 Blouse 开发者_JAVA技巧 Clothing 34.97
123456 Electronica 2002 Music 3.99
123457 Country Tunes Music 21.55
123458 Watermelon Food 8.73
This SQL query returns the most expensive item from each type: SELECT type, MAX(price) FROM products GROUP BY type
Clothing $34.97
Food $8.73
Music $21.55
Toy $89.95
I also want to get the fields id and name that belong to the above max price, for each row. What SQL query will return a table like this?
Id name type price
123455 Blouse Clothing 34.97
123458 Watermelon Food 8.73
123457 Country Tunes Music 21.55
123453 Playstation Toy 89.95
This is the greatest-n-per-group
problem that comes up frequently. My usual way of solving it is logically equivalent to the answer given by @Martin Smith, but does not use a subquery:
SELECT T1.Id, T1.name, T1.type, T1.price
FROM Table T1
LEFT OUTER JOIN Table T2
ON (T1.type = T2.type AND T1.price < T2.price)
WHERE T2.price IS NULL;
My solution and all others given on this thread so far have a chance of producing multiple rows per value of type
, if more than one product shares the same type and both have an equal price that is the max. There are ways to resolve this and break the tie, but you need to tell us which product "wins" in case like that.
You need some other attribute that is guaranteed to be unique over all rows, at least for rows with the same type
. For example, if the product with the greater Id
value should win, you can resolve the tie this way:
SELECT T1.Id, T1.name, T1.type, T1.price
FROM Table T1
LEFT OUTER JOIN Table T2
ON (T1.type = T2.type AND (T1.price < T2.price
OR T1.price = T2.price AND T1.Id < T2.Id))
WHERE T2.price IS NULL;
Edit Just updating mine to meet the clarified requirement
SELECT Id, name, type,price
FROM Table T1
WHERE NOT EXISTS(
SELECT * FROM TABLE T2
WHERE T1.type=t2.type
AND T2.Price >= T1.Price
AND T2.Id > T1.Id
)
You can do it with a subselect
SELECT id, name, type, price FROM products p1
WHERE EXISTS (Select type, max(price) FROM Products p2
GROUP BY type
WHERE p1.type=p2.type AND p1.price=p2.MAX(price))
or an inner join
SELECT id, name, type, price FROM products p1
INNER JOIN (Select type, max(price) FROM Products p2 GROUP BY type) maxPrice
ON maxPrice=price=p1.price AND maxPrice.type=p1.price
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