Обсуждение: syntax of joins
hi, is there a disadvantage to write a join as select * from a, b where a.id = b.a_id; over select * from a join b on a.id = b.a_id;
Hello 2012/4/6 Andreas <maps.on@gmx.net>: > hi, > > is there a disadvantage to write a join as > > select * > from a, b > where a.id = b.a_id; > > over > > select * > from a join b on a.id = b.a_id; > yes - newer notation has some advantages * clean specification join predicate and filter predicate * simple adaptability to outer join * increased protection against copy/paste bug that introduce Cartesian product Regards Pavel Stehule > -- > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-sql
On 04/06/2012 01:23 PM, Pavel Stehule wrote: > Hello > > 2012/4/6 Andreas<maps.on@gmx.net>: >> hi, >> >> is there a disadvantage to write a join as >> >> select * >> from a, b >> where a.id = b.a_id; >> > >> over >> >> select * >> from a join b on a.id = b.a_id; >> > > yes - newer notation has some advantages > > * clean specification join predicate and filter predicate > * simple adaptability to outer join > * increased protection against copy/paste bug that introduce Cartesian product > > Regards > > Pavel Stehule > >> -- >> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) >> To make changes to your subscription: >> http://www.postgresql.org/mailpref/pgsql-sql > In other words, no disadvantage :) -some cranky old guy who still misses "retrieve"
2012/4/6 Rob Sargent <robjsargent@gmail.com>: > On 04/06/2012 01:23 PM, Pavel Stehule wrote: >> >> Hello >> >> 2012/4/6 Andreas<maps.on@gmx.net>: >>> >>> hi, >>> >>> is there a disadvantage to write a join as >>> >>> select * >>> from a, b >>> where a.id = b.a_id; >>> >> >>> over >>> >>> select * >>> from a join b on a.id = b.a_id; >>> >> >> yes - newer notation has some advantages >> >> * clean specification join predicate and filter predicate >> * simple adaptability to outer join >> * increased protection against copy/paste bug that introduce Cartesian >> product >> >> Regards >> >> Pavel Stehule >> >>> -- >>> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) >>> To make changes to your subscription: >>> http://www.postgresql.org/mailpref/pgsql-sql >> >> > In other words, no disadvantage :) > Hard to say - for man who fixed critical cartesian products :) in queries Pavel > -some cranky old guy who still misses "retrieve" > > > -- > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-sql
On 04/06/2012 01:46 PM, Pavel Stehule wrote: > 2012/4/6 Rob Sargent<robjsargent@gmail.com>: >> On 04/06/2012 01:23 PM, Pavel Stehule wrote: >>> >>> Hello >>> >>> 2012/4/6 Andreas<maps.on@gmx.net>: >>>> >>>> hi, >>>> >>>> is there a disadvantage to write a join as >>>> >>>> select * >>>> from a, b >>>> where a.id = b.a_id; >>>> >>> >>>> over >>>> >>>> select * >>>> from a join b on a.id = b.a_id; >>>> >>> >>> yes - newer notation has some advantages >>> >>> * clean specification join predicate and filter predicate >>> * simple adaptability to outer join >>> * increased protection against copy/paste bug that introduce Cartesian >>> product >>> >>> Regards >>> >>> Pavel Stehule >>> >>>> -- >>>> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) >>>> To make changes to your subscription: >>>> http://www.postgresql.org/mailpref/pgsql-sql >>> >>> >> In other words, no disadvantage :) >> > > Hard to say - for man who fixed critical cartesian products :) in queries > > Pavel but doesn't there remain "a join b on a.id != b.id" (I do use the join syntax -- sometimes, honest) rjs