MySQL SQL Query Help

I have a table:

id fkid foo bar
1 1 345 yellow
2 1 34 red
3 2 3459 green
4 2 345 brown

I want to select the largest value of "foo" for a unique fkid, and return
bar, the results ordered by bar. In this case, 345 is the largest value of
foo for fkid 1, and 3459 is the largest for fkid 2. "green" comes before
"yellow." My desired result set would be:

fkid foo bar
2 3459 green
1 345 yellow

How would I write that in SQL? fkid and foo are ints, bar is a varchar.

Beckman
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Peter Beckman Internet Guy
beckman@purplecow.com http://www.purplecow.com/
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RE: MySQL SQL Query Help

select max(bar) from mytable where unique fkid order by bar asc

as far as I remember!!

-----Original Message-----
From: Peter Beckman [mailto:beckman@purplecow.com]
Sent: Lunes, 13 de Noviembre de 2006 04:59 p.m.
To: PHP-DB Mailing List
Subject: [PHP-DB] MySQL SQL Query Help


I have a table:

id fkid foo bar
1 1 345 yellow
2 1 34 red
3 2 3459 green
4 2 345 brown

I want to select the largest value of "foo" for a unique fkid, and return
bar, the results ordered by bar. In this case, 345 is the largest value of
foo for fkid 1, and 3459 is the largest for fkid 2. "green" comes before
"yellow." My desired result set would be:

fkid foo bar
2 3459 green
1 345 yellow

How would I write that in SQL? fkid and foo are ints, bar is a varchar.

Beckman
------------------------------------------------------------ ---------------
Peter Beckman Internet Guy
beckman@purplecow.com http://www.purplecow.com/
------------------------------------------------------------ ---------------

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Re: MySQL SQL Query Help

Hi

Try:

SELECT fkid, MAX(foo), bar FROM table GROUP BY fkid ORDER BY bar DESC

Niel

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Re: MySQL SQL Query Help

Actually, that should not work, it should give you an error.

This should work:

SELECT `fkid`,max(`foo`) as foo,`bar` FROM `test2` GROUP BY `fkid` ORDER BY `bar` ASC



Miguel Guirao wrote:
> select max(bar) from mytable where unique fkid order by bar asc
>
> as far as I remember!!
>
> -----Original Message-----
> From: Peter Beckman [mailto:beckman@purplecow.com]
> Sent: Lunes, 13 de Noviembre de 2006 04:59 p.m.
> To: PHP-DB Mailing List
> Subject: [PHP-DB] MySQL SQL Query Help
>
>
> I have a table:
>
> id fkid foo bar
> 1 1 345 yellow
> 2 1 34 red
> 3 2 3459 green
> 4 2 345 brown
>
> I want to select the largest value of "foo" for a unique fkid, and return
> bar, the results ordered by bar. In this case, 345 is the largest value of
> foo for fkid 1, and 3459 is the largest for fkid 2. "green" comes before
> "yellow." My desired result set would be:
>
> fkid foo bar
> 2 3459 green
> 1 345 yellow
>
> How would I write that in SQL? fkid and foo are ints, bar is a varchar.
>
> Beckman
> ------------------------------------------------------------ ---------------
> Peter Beckman Internet Guy
> beckman@purplecow.com http://www.purplecow.com/
> ------------------------------------------------------------ ---------------
>
>

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Re: MySQL SQL Query Help

On Mon, 13 Nov 2006, bluefx13@gmail.com wrote:

> Actually, that should not work, it should give you an error.
>
> This should work:
>
> SELECT `fkid`,max(`foo`) as foo,`bar` FROM `test2` GROUP BY `fkid` ORDER BY `bar` ASC

Yes, but if the data is in a different order that fails and doesn't maintain row order:

mysql> create temporary table test2 (id tinyint,fkid tinyint, foo smallint, bar varchar(20));
mysql> insert into test2 values (1,1,34,'red'), (2,1,345,'yellow'), (3,2,345,'brown'), (4,2,3459,'green');
mysql> select * from test2;
+------+------+------+--------+
| id | fkid | foo | bar |
+------+------+------+--------+
| 1 | 1 | 34 | red |
| 2 | 1 | 345 | yellow |
| 3 | 2 | 345 | brown |
| 4 | 2 | 3459 | green |
+------+------+------+--------+
mysql> SELECT `fkid`,max(`foo`) as foo,`bar` FROM `test2` GROUP BY `fkid` ORDER BY `bar` ASC;
+------+------+-------+
| fkid | foo | bar |
+------+------+-------+
| 2 | 3459 | brown |
| 1 | 345 | red |
+------+------+-------+
2 rows in set (0.00 sec)

Notice how 3459 is supposed to be green but reports brown, and 345 should
be yellow but reports red?

Any other solutions that maintain row integrity?

Beckman

> Miguel Guirao wrote:
>> select max(bar) from mytable where unique fkid order by bar asc
>>
>> as far as I remember!!
>>
>> -----Original Message-----
>> From: Peter Beckman [mailto:beckman@purplecow.com]
>> Sent: Lunes, 13 de Noviembre de 2006 04:59 p.m.
>> To: PHP-DB Mailing List
>> Subject: [PHP-DB] MySQL SQL Query Help
>>
>>
>> I have a table:
>>
>> id fkid foo bar
>> 1 1 345 yellow
>> 2 1 34 red
>> 3 2 3459 green
>> 4 2 345 brown
>>
>> I want to select the largest value of "foo" for a unique fkid, and return
>> bar, the results ordered by bar. In this case, 345 is the largest value of
>> foo for fkid 1, and 3459 is the largest for fkid 2. "green" comes before
>> "yellow." My desired result set would be:
>>
>> fkid foo bar
>> 2 3459 green
>> 1 345 yellow
>>
>> How would I write that in SQL? fkid and foo are ints, bar is a varchar.
>>
>> Beckman
>> ------------------------------------------------------------ ---------------
>> Peter Beckman Internet Guy
>> beckman@purplecow.com http://www.purplecow.com/
>> ------------------------------------------------------------ ---------------
>>
>>
>
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> PHP Database Mailing List (http://www.php.net/)
> To unsubscribe, visit: http://www.php.net/unsub.php
>

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Peter Beckman Internet Guy
beckman@purplecow.com http://www.purplecow.com/
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Re: MySQL SQL Query Help

Peter Beckman wrote:
> On Mon, 13 Nov 2006, bluefx13@gmail.com wrote:
>
>> Actually, that should not work, it should give you an error.
>>
>> This should work:
>>
>> SELECT `fkid`,max(`foo`) as foo,`bar` FROM `test2` GROUP BY `fkid`
>> ORDER BY `bar` ASC
>
> Yes, but if the data is in a different order that fails and doesn't
> maintain row order:
>
> mysql> create temporary table test2 (id tinyint,fkid tinyint, foo
> smallint, bar varchar(20));
> mysql> insert into test2 values (1,1,34,'red'), (2,1,345,'yellow'),
> (3,2,345,'brown'), (4,2,3459,'green');
> mysql> select * from test2;
> +------+------+------+--------+
> | id | fkid | foo | bar |
> +------+------+------+--------+
> | 1 | 1 | 34 | red |
> | 2 | 1 | 345 | yellow |
> | 3 | 2 | 345 | brown |
> | 4 | 2 | 3459 | green |
> +------+------+------+--------+
> mysql> SELECT `fkid`,max(`foo`) as foo,`bar` FROM `test2` GROUP BY
> `fkid` ORDER BY `bar` ASC;
> +------+------+-------+
> | fkid | foo | bar |
> +------+------+-------+
> | 2 | 3459 | brown |
> | 1 | 345 | red |
> +------+------+-------+
> 2 rows in set (0.00 sec)
>
> Notice how 3459 is supposed to be green but reports brown, and 345 should
> be yellow but reports red?
>
> Any other solutions that maintain row integrity?

You might have to go a subquery.

(I'm not great at subqueries so there would have to be a better way to
write this anyway).

This works in postgresql:

select fkid, foo, bar from test2 t2 where (select max(foo) from test2 t1
where t1.fkid=t2.fkid)=foo;


but mysql won't let you reference the same table inside & outside:

mysql> select fkid, foo, bar from test2 t2 where (select max(foo) from
test2 t1 where t1.fkid=t2.fkid)=foo;
ERROR 1137 (HY000): Can't reopen table: 't2'

http://dev.mysql.com/doc/refman/5.0/en/subqueries.html

The mysql mailing list might have better ideas..

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