Hi,



I've just finished reading about datasets in my ASP.NET book. I understand

that its nice to keep certain tables in a dataset so you can work with them

and reference them etc. But why the heck do I need to specify relationships

between these tables. If I want to join two tables, isn't it just

easier/better performance for me to use a query and return those results as

a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

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It's useful if you need to create some tables in memory.



-----Original Message-----

From: Greg Quinn [mailto:greg@i...]

Sent: maandag 28 januari 2002 20:39

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???





Hi,



I've just finished reading about datasets in my ASP.NET book. I

understand that its nice to keep certain tables in a dataset so you can

work with them and reference them etc. But why the heck do I need to

specify relationships between these tables. If I want to join two

tables, isn't it just easier/better performance for me to use a query

and return those results as a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

I think it may apply to a parent child relationship between tables, like

invoice header and invoice items.  I'm reaching a point in a current

project where I will get to try this out and then I'll know for sure. 

_____________________________________________



Kyle Dunn

Chief Information Officer

Funeral Services, Inc.

xxx-xxx-xxxx  x 309

Kyle@F...



-----Original Message-----

From: Greg Quinn [mailto:greg@i...]

Sent: Monday, January 28, 2002 2:39 PM

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???



Hi,



I've just finished reading about datasets in my ASP.NET book. I

understand

that its nice to keep certain tables in a dataset so you can work with

them

and reference them etc. But why the heck do I need to specify

relationships

between these tables. If I want to join two tables, isn't it just

easier/better performance for me to use a query and return those results

as

a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

Greg,



If you are retrieving results from different SQL Servers you can store

your multiple result sets in the dataset and then build a relationship

which will allow you to further refine what you want displayed.



Mark





-----Original Message-----

From: Greg Quinn [mailto:greg@i...] 

Sent: Monday, January 28, 2002 1:39 PM

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???





Hi,



I've just finished reading about datasets in my ASP.NET book. I

understand that its nice to keep certain tables in a dataset so you can

work with them and reference them etc. But why the heck do I need to

specify relationships between these tables. If I want to join two

tables, isn't it just easier/better performance for me to use a query

and return those results as a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

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this format, some or all of this message may not be legible.



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You are correct in thinking that there is a bunch of hype for a feature that

me never be used; however, I think that comes form our "We never needed this

before" mindset.  I said the same thing when I started into DataSets.



Here is my thoughts on it;



1.  If you are really into disconnected data, like .NET, then some way to

create and maintain data integrity is very useful.  By establishing

relationships and constraints in the DataSet, we don't have to worry about

tracking these things in our code.  



2.  You can think of Related Tables in a DataSet as linked lists.  That

would make coding hierarchical data easier to manage.



3.  Disparate Data Sources, such as customers in SQL Server, and Orders in

MySQL (It could happen ;), but you still need to maintain the data

integrity.



So my reasoning is that Data Integrity is the big gain from it.  Speed on

the other hand is not.  If all you want to do is join the data in two

tables, the a Query is better than a DataSet with relations defined.



tc





-----Original Message-----

From: Greg Quinn [mailto:greg@i...] 

Sent: Monday, January 28, 2002 1:39 PM

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???



Hi,



I've just finished reading about datasets in my ASP.NET book. I understand

that its nice to keep certain tables in a dataset so you can work with them

and reference them etc. But why the heck do I need to specify relationships

between these tables. If I want to join two tables, isn't it just

easier/better performance for me to use a query and return those results as

a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

Joins = More rows, More rows = more memory! I also like what others said on

different data sources.



Regards,

Dave



-----Original Message-----

From: Greg Quinn [mailto:greg@i...]

Sent: Monday, January 28, 2002 1:39 PM

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???





Hi,



I've just finished reading about datasets in my ASP.NET book. I understand

that its nice to keep certain tables in a dataset so you can work with them

and reference them etc. But why the heck do I need to specify relationships

between these tables. If I want to join two tables, isn't it just

easier/better performance for me to use a query and return those results as

a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

Joins don't necessarily mean more rows, just more processing than single

table selects (at least for the DB Server).



tc





-----Original Message-----

From: Dave Buckner [mailto:Dave@N...] 

Sent: Monday, January 28, 2002 11:16 AM

To: ASP+

Subject: [aspx] RE: Datasets - whats so good about the relationships???



Joins = More rows, More rows = more memory! I also like what others said on

different data sources.



Regards,

Dave



-----Original Message-----

From: Greg Quinn [mailto:greg@i...]

Sent: Monday, January 28, 2002 1:39 PM

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???





Hi,



I've just finished reading about datasets in my ASP.NET book. I understand

that its nice to keep certain tables in a dataset so you can work with them

and reference them etc. But why the heck do I need to specify relationships

between these tables. If I want to join two tables, isn't it just

easier/better performance for me to use a query and return those results as

a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

All rows returned though from the server in most cases generate more rows

then when not joining a table. Most of the time this is due to multi child

records. yes?



Dave



-----Original Message-----

From: ToddC@m... [mailto:ToddC@m...]

Sent: Monday, January 28, 2002 11:24 AM

To: ASP+

Subject: [aspx] RE: Datasets - whats so good about the relationships?? ?





Joins don't necessarily mean more rows, just more processing than single

table selects (at least for the DB Server).



tc





-----Original Message-----

From: Dave Buckner [mailto:Dave@N...]

Sent: Monday, January 28, 2002 11:16 AM

To: ASP+

Subject: [aspx] RE: Datasets - whats so good about the relationships???



Joins = More rows, More rows = more memory! I also like what others said on

different data sources.



Regards,

Dave



-----Original Message-----

From: Greg Quinn [mailto:greg@i...]

Sent: Monday, January 28, 2002 1:39 PM

To: ASP+

Subject: [aspx] Datasets - whats so good about the relationships???





Hi,



I've just finished reading about datasets in my ASP.NET book. I understand

that its nice to keep certain tables in a dataset so you can work with them

and reference them etc. But why the heck do I need to specify relationships

between these tables. If I want to join two tables, isn't it just

easier/better performance for me to use a query and return those results as

a table in my dataset?



Please can someone explain to me why I would ever need to specify the

relationships between tables in a dataset, and give me some real-world

examples of what benefit this brings...



Thanks

Greg

I agree with Todd - for instance say for our first schema we have 2 tables 

in where the second table has a relationship with the first based upon the 

customer name (just an example - having keys as varchar's is not optimal):



tblCustomer

-----------

1 record: "Test Customer"



tblCreditCards

-----------

1 record: "Test Customer", "Visa"

1 record: "Test Customer", "Master Card"

1 record: "Test Customer", "Discover"



or for the second just one denormalized table as:



tblCustomer

-----------

1 record: "Test Customer", "Visa"

1 record: "Test Customer", "Master Card"

1 record: "Test Customer", "Discover"



in this example if I do a join on the first schema or a single select on the 

second I always get back 3 rows, so just because you have a join (in this 

case an inner) doesn't mean your gonna get back more rows....



>From: "Dave Buckner" <Dave@N...>

>Reply-To: "ASP+" <aspx@p...>

>To: "ASP+" <aspx@p...>

>Subject: [aspx] RE: Datasets - whats so good about the relationships??     

>?

>Date: Mon, 28 Jan 2002 12:22:59 -0600

>

>All rows returned though from the server in most cases generate more rows

>then when not joining a table. Most of the time this is due to multi child

>records. yes?

>

>Dave

>

>-----Original Message-----

>From: ToddC@m... [mailto:ToddC@m...]

>Sent: Monday, January 28, 2002 11:24 AM

>To: ASP+

>Subject: [aspx] RE: Datasets - whats so good about the relationships?? ?

>

>

>Joins don't necessarily mean more rows, just more processing than single

>table selects (at least for the DB Server).

>

>tc

>

>

>-----Original Message-----

>From: Dave Buckner [mailto:Dave@N...]

>Sent: Monday, January 28, 2002 11:16 AM

>To: ASP+

>Subject: [aspx] RE: Datasets - whats so good about the relationships???

>

>Joins = More rows, More rows = more memory! I also like what others said on

>different data sources.

>

>Regards,

>Dave

>

>-----Original Message-----

>From: Greg Quinn [mailto:greg@i...]

>Sent: Monday, January 28, 2002 1:39 PM

>To: ASP+

>Subject: [aspx] Datasets - whats so good about the relationships???

>

>

>Hi,

>

>I've just finished reading about datasets in my ASP.NET book. I understand

>that its nice to keep certain tables in a dataset so you can work with them

>and reference them etc. But why the heck do I need to specify relationships

>between these tables. If I want to join two tables, isn't it just

>easier/better performance for me to use a query and return those results as

>a table in my dataset?

>

>Please can someone explain to me why I would ever need to specify the

>relationships between tables in a dataset, and give me some real-world

>examples of what benefit this brings...

>

>Thanks

>Greg

>

>




>

>

>

>




>




>

>

>

>












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