[GENERAL] How to select rows that are the max for each subcategory?
Suppose I have a table T that has, among its columns, the fields X and Y, where Y is an integer, and multiple rows with the same value of X are possible. I want to select the rows corresponding to the greatest values of Y for each value of X. E.g. suppose that T is X Y Z a 1 eenie a 3 meenie a 2 miny b 4 moe b 0 catch ...the result of the desired query would be a 3 meenie b 4 moe TIA! Kynnjo
Re: [GENERAL] How to select rows that are the max for each subcategory?
select x,y,z from t join (select x, max(y) as my from t group by x) t1 on (t.x=t1.x and t.y=t1.my) best wishes Harald On Thu, Sep 25, 2008 at 20:01, Kynn Jones <[EMAIL PROTECTED]> wrote: > Suppose I have a table T that has, among its columns, the fields X and Y, > where Y is an integer, and multiple rows with the same value of X are > possible. I want to select the rows corresponding to the greatest values of > Y for each value of X. E.g. suppose that T is > X Y Z > a 1 eenie > a 3 meenie > a 2 miny > b 4 moe > b 0 catch > ...the result of the desired query would be > a 3 meenie > b 4 moe > TIA! > Kynnjo > > > -- GHUM Harald Massa persuadere et programmare Harald Armin Massa Spielberger Straße 49 70435 Stuttgart 0173/9409607 no fx, no carrier pigeon - EuroPython 2009 will take place in Birmingham - Stay tuned! -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] How to select rows that are the max for each subcategory?
uups, you need to specify the table in the select, so select t.x,t.y,t.z from t join (select x, max(y) as my from t group by x) t1 on (t.x=t1.x and t.y=t1.my) On Thu, Sep 25, 2008 at 20:05, Harald Armin Massa <[EMAIL PROTECTED]> wrote: > select x,y,z > from > t join (select x, max(y) as my from t group by x) t1 on (t.x=t1.x and > t.y=t1.my) > > best wishes > > Harald > > On Thu, Sep 25, 2008 at 20:01, Kynn Jones <[EMAIL PROTECTED]> wrote: >> Suppose I have a table T that has, among its columns, the fields X and Y, >> where Y is an integer, and multiple rows with the same value of X are >> possible. I want to select the rows corresponding to the greatest values of >> Y for each value of X. E.g. suppose that T is >> X Y Z >> a 1 eenie >> a 3 meenie >> a 2 miny >> b 4 moe >> b 0 catch >> ...the result of the desired query would be >> a 3 meenie >> b 4 moe >> TIA! >> Kynnjo >> >> >> > > > > -- > GHUM Harald Massa > persuadere et programmare > Harald Armin Massa > Spielberger Straße 49 > 70435 Stuttgart > 0173/9409607 > no fx, no carrier pigeon > - > EuroPython 2009 will take place in Birmingham - Stay tuned! > -- GHUM Harald Massa persuadere et programmare Harald Armin Massa Spielberger Straße 49 70435 Stuttgart 0173/9409607 no fx, no carrier pigeon - EuroPython 2009 will take place in Birmingham - Stay tuned! -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] How to select rows that are the max for each subcategory?
"Kynn Jones" <[EMAIL PROTECTED]> writes: > Suppose I have a table T that has, among its columns, the fields X and Y, > where Y is an integer, and multiple rows with the same value of X are > possible. I want to select the rows corresponding to the greatest values of > Y for each value of X. You could use DISTINCT ON --- see the "weather reports" example in the SELECT reference page. It's not standard SQL but will usually be faster than solutions that use only standard features. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] How to select rows that are the max for each subcategory?
Thank you all! Kynn
