[hibernate-dev] 6.0 - formalized standard functions

[Steve Ebersole]

Thanks for reply Christian..


On Wed, May 31, 2017 at 7:18 AM Christian Beikov <christian.beikov at gmail.com>
wrote:

> Looks good. OTOH I'd also like to see the following functions
>
>   * millisecond_diff
>   * second_diff
>   * minute_diff
>   * hour_diff
>   * day_diff
>   * week_diff
>   * month_diff
>   * quater_diff
>   * year_diff
>

Why not basic temporal arithmetic?  E.g. `second(x) - second(y)` (which
isgenerally resolved to `extract(second from x) - extract(second from y)`...



>   * epoch - generally defined as `extract(epoch from ?1)`
>

Because ANSI SQL does not define epoch as an extractable part of a
temporal. TBH I do not think it defines milliseconds as extractable either
but would have to check.  Also, I am not sure of databases that support
that, nor any alternate (which we'd *need* to support this as a standard
func) for databases which do not.

  * group_concat - string aggregation function
>

How is this different from concat()?


> The group_concat function would probably be not be possible to implement
> for all DBMS, but at least the bigger ones have one or the other
> function that could be used to implement this.
>

Unless I am missing something in your idea here (which is why I asked
above) we can absolutely implement this on all databases - everyone has a
concat operator as well.  And a SQM/SQL-AST function need not evaluate to a
db function - it just needs to be an expression.


> Don't know what is best regarding the "str" function.


`str()` is defined as `cast`; that's not the issue.  The issue is merely
the type - I am simply arguing that VARCHAR is more correct