Perl 6 Junctions and Postgres SQL

[mugwumpjism]

I noticed that PostgreSQL and Perl 6 have the same syntax for junctions (well, at least any)

samv=# select s from generate_series(1,20) s where s = any (select y f
+rom generate_series(18,23) y)
;
 s  
----
 18
 19
 20
(3 rows)

This year's perl:

perl -MPerl6::Junction=any -le 'for my $s (1..20) { if ($s == any(18..23) ) { print $s } }'

[dragonchild]

In other words, PostgreSQL provides an alias for "WHERE s IN (...)" and calls it "WHERE s = ANY(...)". Forgive me for being underwhelmed.

It's not surprising that SQL is going to look at a lot like the junction operators - both operate on sets^*. A relational database is nothing more than a set theory machine. The junction operators are similar. You even have all() and one() in SQL; they're just not in the forms you're thinking of.

*: Yes, the junction operators deal with lists, but they treat the lists as sets.

[grinder]

I share your sentiments. Still, all is not lost. I was happy to hear of the generate_series thing. I don't know how directly this can be transposed to another DB, (thinking of Oracle here), but I do know that at times it can be nice to have a select generate a huge amount of arbitary data on the fly.

The other day I needed to blend the numbers 1..19999 into a select, and after considering a select ... union select from dual for about a microsecond, I created a table with a single column containing the numbers from 1 to 19999. Sort of ugly, but it got the job done.

[perlostitute]

How so?

[mugwumpjism]

Ok, piece by piece:

(select y from generate_series(18,23) y)
(select s from generate_series(1,20) s)

Is similar to, respectively:

(18..23)
(1..20)

Then this query:

select s from (1..20) where s = any( 18..23 )

Is similar in meaning to this:

for my $s (1..20) {
    if ($s == any(18..23) ) {
        print $s;
    }
}

Or, more close in expression to the SQL, the Perl 6:

[1..20].grep:{ $_ == any(18..23) }.say

Hmm, wouldn't it be useful to have a LINQ to Hyper-operator/Junction cheat-sheet...

[rhesa]

Toying with perl 5.10:

perl -E 'for(1..20) { when([18..23]) { say } }'

:-)

I'm slightly puzzled that I couldn't write when(18..23), though.