po 25. 11. 2019 v 20:32 odesílatel Phil Florent <philflor...@hotmail.com> napsal:
> Hi, > > We are still on the process to migrate our applications from proprietary > RDBMS to PostgreSQL. > > Here is a simple query executed on various systems (real query is > different but this one does not need any data) : > > Connected to: > > Oracle Database 19c Standard Edition 2 Release 19.0.0.0.0 - Production > > Version 19.3.0.0.0 > > > > SQL> select count(*) from (select 1 from dual where 0=1 group by grouping > sets(())) tmp; > > > > COUNT(*) > > ---------- > > 0 > > > > > > select @@version; > > GO > > > > > --------------------------------------------------------------------------------------------------------------------------- > --------------------------------------------------------------------------------------------------------------------------- > ------------------------------------------------------ > > Microsoft SQL Server 2017 (RTM-CU16) (KB4508218) - 14.0.3223.3 (X64) > > Jul 12 2019 17:43:08 > > Copyright (C) 2017 Microsoft Corporation > > Developer Edition (64-bit) on Linux (Ubuntu 16.04.6 LTS) > > > > select count(*) from (select 1 as c1 where 0=1 group by grouping sets(())) > tmp; > > GO > > > > ----------- > > 0 > > > > (1 rows affected) > > > > > > select version(); > > version > > > ---------------------------------------------------------------------------------------------------------------- > > PostgreSQL 11.5 (Debian 11.5-1+deb10u1) on x86_64-pc-linux-gnu, compiled > by gcc (Debian 8.3.0-6) 8.3.0, 64-bit > > > > > > > > select count(*) from (select 1 from dual where 0=1 group by grouping > sets(())) tmp; > > count > > ------- > > 1 > > (1 ligne) > > > > > > 0 or 1, which behaviour conforms to the SQL standard ? We have a > workaround and it's just informational. > This example has not too much sense - I am not sure if these corner cases are described by ANSI SQL standards. If I add aggregate query to subquery - using grouping sets without aggregation function is strange, then Postgres result looks more correct postgres=# select 1, count(*) from dual group by grouping sets(()); ┌──────────┬───────┐ │ ?column? │ count │ ╞══════════╪═══════╡ │ 1 │ 1 │ └──────────┴───────┘ (1 row) postgres=# select 1, count(*) from dual where false group by grouping sets(()); ┌──────────┬───────┐ │ ?column? │ count │ ╞══════════╪═══════╡ │ 1 │ 0 │ └──────────┴───────┘ (1 row) SELECT count(*) from this should be one in both cases. I am not sure, if standard describe using grouping sets without any aggregation function Pavel > > Regards, > > > Phil > >
