Or you could do something really fancy....
https://en.wikipedia.org/wiki/Z-order_curve
http://www.forceflow.be/2013/10/07/morton-encodingdecoding-through-bit-interleaving-implementations/
- (x,y,z) = *(5,9,1)* = (0101,1001,0001)
- Interleaving the bits results in: 010001000111 = *1095* th cell along
the Z-curve.
doesn't have to be base 2 merging, could use base10 digits and merge them
interleaving....
(a,b) = (123, 567)
merged = 152637
Although for simpliicty simply combining them with a separator character
would work too....
if you don't have a separator (1,111) would look the same as (111,1)
On Fri, Oct 20, 2017 at 1:17 PM, Eugene Mirotin <emiro...@gmail.com> wrote:
> Yeah, use two FKs, then you can obtain this "combined" value on select:
>
> select printf("%s-%s", student_id, workpiecelist_id) as id from
> uniqueworkpc
>
> On Fri, Oct 20, 2017 at 11:05 PM David Raymond <david.raym...@tomtom.com>
> wrote:
>
> > I don't know about automatically, but you can use foreign keys to help.
> >
> > create table student (
> > student_id integer primary key,
> > blah
> > );
> > create table workpiecelist (
> > workpiecelist_id integer primary key,
> > blah
> > );
> >
> > create table uniqueworkpc (
> > student_id int references student,
> > workpiecelist_id int references workpieceList,
> > blah,
> > primary key (student_id, workpiecelist_id)
> > );
> >
> >
> >
> > -----Original Message-----
> > From: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org]
> > On Behalf Of csanyipal
> > Sent: Friday, October 20, 2017 3:57 PM
> > To: sqlite-users@mailinglists.sqlite.org
> > Subject: [sqlite] How to create primary key from two another PK's?
> >
> > Hi,
> >
> > I have a small and simple database MyStudents.db .
> > It has three tables: *student*, *workpiecelist*, *uniqueworkpc*.
> > How can I manage to get primary key (pk) automatically for *uniqueworkpc*
> > table which is composed by pk of *student* table and pk of
> *workpiecelist*
> > table like below?
> > 03256789415632-2
> > where
> > 03256789415632
> > is a pk of a student in *student* table, and
> > 2
> > is an id of a workpiece in *workpiecelist* table.
> >
> >
> >
> > -----
> > Best, Pál
> > --
> > Sent from: http://sqlite.1065341.n5.nabble.com/
> > _______________________________________________
> > sqlite-users mailing list
> > sqlite-users@mailinglists.sqlite.org
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> > sqlite-users mailing list
> > sqlite-users@mailinglists.sqlite.org
> > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
> >
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