many to many self join

  • Thread starter Thread starter thadson
  • Start date Start date
T

thadson

I'm faced with a unique problem.
many-to-many self join
I have a list of drawings. some drawings include subdrawings and those
subdrawings can have more subdrawings. However, the subdrawings can be main
drawings for a project by themselves.

It looks like this:
I have projects. I put them into tbl_projects
I have drawings for above projects. tbl_drawings
now some drawings belong to some drawings.

router1 - box1 - feet1
- button1
- mainboard - powersupplyboard1
-antenna

router2 - box1 - feet2
- button1
- mainboard - powersupplyboard2
- antenna2

switch1 - box1 - feet1
- button2
- mainboard - powersupplyboard1

In plain words, a there are many routers, all can have the same or different
looking boxes. All boxes can have the same or different feet, switches,
mainboards, etc...
Than all mainboards have parts on them, like capacitors and resistors, but
can have complex parts that are described in more drawings like the
powersupply which in turn could have its own enclosure and feet drawing that
could be the same or different from the above. Even writing it down seems
complex and confusing.

Any idea how I can self join the drawings so any drawing can belong to any
other drawing in any depth?

Thanks for any help.
 
I'm faced with a unique problem.
many-to-many self join
I have a list of drawings. some drawings include subdrawings and those
subdrawings can have more subdrawings. However, the subdrawings can be main
drawings for a project by themselves.

It looks like this:
I have projects.  I put them into tbl_projects
I have drawings for above projects. tbl_drawings
now some drawings belong to some drawings.

router1 - box1 - feet1
                      - button1
          - mainboard - powersupplyboard1
                             -antenna

router2 - box1 - feet2
                     - button1
           - mainboard - powersupplyboard2
                             - antenna2

switch1 - box1 - feet1
                      - button2
          - mainboard - powersupplyboard1

In plain words, a there are many routers, all can have the same or different
looking boxes. All boxes can have the same or different feet, switches,
mainboards, etc...
Than all mainboards have parts on them, like capacitors and resistors, but
can have complex parts that are described in more drawings like the
powersupply which in turn could have its own enclosure and feet drawing that
could be the same or different from the above. Even writing it down seems
complex and confusing.

Any idea how I can self join the drawings so any drawing can belong to any
other drawing in any depth?

Thanks for any help.
Click to expand...

Out of time, but this should probably continue with a tbl_contains
table for a many-to-many relationship:
Project_ID,Contains_ID,Parent_ID,Child_ID
1,1,'router1','box1'
1,2,'box1','feet1'
1,3,'box1','button1'
etc.
primary key(Project_ID,Contains_ID)
nonunique index (Parent_ID)
nonunique index (Child_ID)

To get full dataset in each row by project you may need to use a union
with increasing levels of self joins in each select. Hopefully you
don't need to see the data that way, but it's possible.

Jeff
 
Thadson this post helped me

as well as this sample DB
Here's a sample database that illustrates the technique:
http://www.mvps.org/access/modules/mdl0027.htm

Subject: Re: Grouping components and updating locations 10/10/2008 8:34 AM
PST

By: Barry A&P In: microsoft.public.access.tablesdbdesign


Allen
this query worked for me

SELECT Parent3PartNumbers.[Part Number], Parent3PartNumbers.Description,
Parent3.[Serial Number], Parent2PartNumbers.[Part Number],
Parent2PartNumbers.Description, Parent2.[Serial Number],
Parent1PartNumbers.[Part Number], Parent1PartNumbers.Description,
Parent1.[Serial Number], PartNumbers.[Part Number], PartNumbers.Description,
Parts.[Serial Number], PartNumbers.PartNumberID
FROM ((PartNumbers AS Parent2PartNumbers RIGHT JOIN (PartNumbers AS
Parent3PartNumbers RIGHT JOIN (((SerialNumbers AS Parts LEFT JOIN
SerialNumbers AS Parent1 ON Parts.SNParentID = Parent1.SerialNumberID) LEFT
JOIN SerialNumbers AS Parent2 ON Parent1.SNParentID = Parent2.SerialNumberID)
LEFT JOIN SerialNumbers AS Parent3 ON Parent2.SNParentID =
Parent3.SerialNumberID) ON Parent3PartNumbers.PartNumberID =
Parent3.PartNumberID) ON Parent2PartNumbers.PartNumberID =
Parent2.PartNumberID) LEFT JOIN PartNumbers AS Parent1PartNumbers ON
Parent1.PartNumberID = Parent1PartNumbers.PartNumberID) LEFT JOIN PartNumbers
ON Parts.PartNumberID = PartNumbers.PartNumberID
ORDER BY Parent3PartNumbers.[Part Number], Parent3.[Serial Number],
Parent2PartNumbers.[Part Number], Parent2.[Serial Number],
Parent1PartNumbers.[Part Number], Parent1.[Serial Number], PartNumbers.[Part
Number], Parts.[Serial Number];

Now i just have to figure out how to use the tree data in the query,
Thank you for getting me on the right track..



Allen Browne said:
Hi Barry

You need to use outer joins to get the records to show up.

Double-click the line joining the 2 tables in the upper pane of the query
design window. Access pops up a dialog offering 3 options. You have to
choose either the 2nd or 3rd one (depending which way round your tables
are), not the first one.

The 2nd part of this article has a brief explanation of outer joins:
The Query Lost My Records!
at:
http://allenbrowne.com/casu-02.html
--
Allen Browne - Microsoft MVP. Perth, Western Australia

Reply to group, rather than allenbrowne at mvps dot org.

Barry A&P said:
Allen
Thank you so much for your help, I was so excited by the simplicity of
your
answer, however i could not get the query to work or the self-join. my
database is as follows (simplified)

Tbl_PartNumbers
PartID Auto# PK
PartName
Life
Cost

Tbl_SerialNumbers
SerNoID Auto# PK
PartID (Lookup to Tbl_PartNumbers)
SerNoparentID
Location

Here is where My Query ended up
SELECT PartNumbers.[Part Number], PartNumbers.Description,
SerialNumbers.[Serial Number], Sub.PartNumberID, Sub.[Serial Number], [Sub
Sub].PartNumberID, [Sub Sub].[Serial Number], [Sub Sub Sub].PartNumberID,
[Sub Sub Sub].[Serial Number]
FROM PartNumbers INNER JOIN (SerialNumbers AS [Sub Sub Sub] INNER JOIN
(SerialNumbers AS [Sub Sub] INNER JOIN (SerialNumbers AS Sub INNER JOIN
SerialNumbers ON Sub.SNParentID = SerialNumbers.SerialNumberID) ON [Sub
Sub].SNParentID = Sub.SerialNumberID) ON [Sub Sub Sub].SNParentID = [Sub
Sub].SerialNumberID) ON PartNumbers.PartNumberID =
SerialNumbers.PartNumberID;

It has no values when i opened it
am i way off base?

The SireSireDameSire Query in your horses example was too hard for me to
reverse engineer. i even tried to setup tables with horses names Ect. i
was
able to get the Self-join (two tables with two one-to-manys) but the
query
asked for values when i ran it.. and didnt work.

Thanks Again
Barry

Allen Browne said:
One approach is to place everything in the one table, e.g.:
PartID AutoNumber primary key
PartName Text
ParentPartID Number

You put the major assemblies in the table, leaving ParentPartID blank as
they are not part of anything. Next you enter he sub-assemblies, and in
the
ParentPartID you put the PartID of the assembly it belongs to. Next you
enter each component, and in ParentPartID you enter the sub-assembly it
belongs to. And so on.

This structure (a self-join), copes with any level of embeddedness. It's
really easy to design, really flexible. For example, you can create a
related table to record sales, and its PartID field can relate back to
any
kind of level (that is, you can sell a component, a sub-assembly, a major
assembly, whatever.)

The disadvantage of this approach comes when you try to do things like
building a complete family tree of the parts you offer. You can create a
monster query that does this to about 4 generations, e.g.:
http://allenbrowne.com/ser-06.html
But the problem of infinite recursion arises, e.g. where are part is
wrongly
entered as its own grandparent.

Here's a sample database that illustrates the technique:
http://www.mvps.org/access/modules/mdl0027.htm

Here's some more involved SQL approaches from Joe Celko:
http://www.intelligententerprise.com/001020/celko.shtml
http://www.dbmsmag.com/9603d06.html
http://www.dbmsmag.com/9604d06.html
http://www.dbmsmag.com/9605d06.html
http://www.dbmsmag.com/9606d06.html

BTW, I hear a rumour that the latest SQL Sever (Express?) supports
resolving
this kind of structure better than JET does, but I haven't personally
tested
it.

I am working on a aircraft Parts management database. I am trying to
find a
way to relate or link Major assembly components, Sub assembly
components,
and
components. For example all parts, assemblies, and sub assemblies are
listed
in the tbl_partnumbers they have corresponding records in
tbl_serialnumbers
that also refer to a record in tbl_locations I want to be able to view
a
major-assembly record that will also list all sub-assembies and the
parts
those sub-assemblies contain. I also want to be able to move a
sub-assembly
from one Major-Assembly to another and have all of its parts Follow it.
Or
move a major-assembly between aircraft and have all sub-assemblies and
parts
follow. maybe this can be done by somehow associating the locations,
but i
am
stumped for now.
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