master - detail in one row, details in one extra column

master - detail in one row, details in one extra column

Post by Hans van Let » Sat, 26 Apr 2003 06:09:22



Hi NG,

Two tables having a master - detail relationship.
I wish to have a resultset that has one row for each master record. Each row
also should have an extra column that contains a concatenated string (let's
say comma-separated) of one column of all associated detail records.
I can't get my head around the SQL required to do this. Is this at all
possible?
Thanks in advance for any suggestions.

Hans van Leth.

 
 
 

master - detail in one row, details in one extra column

Post by Joe Celk » Sat, 26 Apr 2003 06:40:13


You can find several ugly, proprietary kludges in the FAQ, but don't do
this.  Read a book and look at First Normal Form.

--CELKO--
 ===========================
 Please post DDL, so that people do not have to guess what the keys,
constraints, Declarative Referential Integrity, datatypes, etc. in your
schema are.

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master - detail in one row, details in one extra column

Post by Hans van Let » Sat, 26 Apr 2003 15:19:39


Goodmorning Joe,

I red the books, even yours. I know what 1NF etc is.
This is just to denormalize some data prior to printing.

Thanks for your reply.
Hans van Leth.



Quote:> You can find several ugly, proprietary kludges in the FAQ, but don't do
> this.  Read a book and look at First Normal Form.

> --CELKO--
>  ===========================
>  Please post DDL, so that people do not have to guess what the keys,
> constraints, Declarative Referential Integrity, datatypes, etc. in your
> schema are.

> *** Sent via Developersdex http://www.developersdex.com ***
> Don't just participate in USENET...get rewarded for it!

 
 
 

master - detail in one row, details in one extra column

Post by Vlad Vissoultche » Sat, 26 Apr 2003 20:44:16


you might want to check out this thread:

http://tinyurl.com/aao8

HTH,
</wqw>



Quote:> Hi NG,

> Two tables having a master - detail relationship.
> I wish to have a resultset that has one row for each master record. Each
row
> also should have an extra column that contains a concatenated string
(let's
> say comma-separated) of one column of all associated detail records.
> I can't get my head around the SQL required to do this. Is this at all
> possible?
> Thanks in advance for any suggestions.

> Hans van Leth.

 
 
 

master - detail in one row, details in one extra column

Post by Joe Celk » Sun, 27 Apr 2003 07:22:28


Quote:>> This is just to denormalize some data prior to printing.  <<

Don't do that. In A C/S system, display is the job of the front end, not
the back end.  If you move the display functions into the database, you
are going to get hit when the front end changes or you have to use the
SQL with another application on a different physical device.  

--CELKO--
 ===========================
 Please post DDL, so that people do not have to guess what the keys,
constraints, Declarative Referential Integrity, datatypes, etc. in your
schema are.

*** Sent via Developersdex http://www.developersdex.com ***
Don't just participate in USENET...get rewarded for it!

 
 
 

1. Selecting from Master/Detail w/ Detail as columns of Master

We have a situation where we have a master/detail relationship as
follows that we would like to report on:

MasterTable (key1, key2, data1, data2, data3)
DetailTable (key1, key2, data1, data2)

where MasterTable.data3 can be joined to DetailTable.key1 giving us n
number of DetailTable rows per 1 MasterTable row.  Example data is:

Master
S, 1, a, b, 17
S, 2, d, e, 19
S, 3, a, g, 32

and

Detail
17, 1, x
17, 2, y
32, 1, s

Here is the problem we must solve.

1)  We want to allow our users to "personalize" their report output by
deciding how to group and sort the data being reported on.  This is
relatively easy as long as all of the data they are grouping and
ordering by comes from one row of a table.  But when this is not the
case,  we need to be able to report on or select data from MasterTable
and DetailTable, effectively showing the DetailTable rows' data as
columns of MasterDetail.  In the above example, we would like to get
something like:

S, 1, a, b, x, y
S, 2, d, e, null, null
S, 3, a, g, s, null

We want to do this so that we can order by data from each table, and
more specifically, multiple rows from the DetailTable.

For example, we would like to report on MasterTable.key1, key2, data1
and data2 AND DetailTable.data1 (once for every row) and ORDER this
select by MasterTable.data1, DetailTable.data1(where DetailTable.key2 =
1), DetailTable.data1(where DetailTable.key2 = 2).

Example output would then be

S, 3, a, g, s, null
S, 1, a, b, x, y
S, 2, d, e, null, null

I've worked on a similar issue before where we wanted to report on rows
of data as if they were columns.  We wrote a little program to loop
through all of the rows of a detail type table, storing them as columns
of a work table that had one column for each possible row in the table.
In this case, however, we knew how many rows were possible.  In my case
now, we have n rows in the DetailTable.  To make it even worse, each row
has a varchar(255) column in it.  So, even if we were to try the other
method, we would be limited to about 7 varchar(255) columns in the work
table.

There are a lot of details that I have left out, but I wanted to keep it
as simple and generic as possible.  Does anyone have any ideas about how
we can solve this problem?   We would appreciate any insight you may
have.   Our latest option is to limit the users to ordering by the first
20 columns or so, thus allowing us to get more like 70 columns in a work
table.  This is still limited, but not as much so.

Thanks a lot.

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