You should be able to use the Client Side API SData (Ajax) calls to fetch the data you need.  

(+) Creating Ajax calls using the Client Side API. - Sage CRM Hints, Tips and Tricks - Sage CRM - Sage City Community

Thank you.

Where should I place the code? On each onchange section for all three fields?

It is best only a function call in the onChange script.  The function can then be defined in either to Content of the screen or within a script file added to the custom script folder.    This is an otherview of Client Side API Sage CRM : Ten Easy Ways to Use the Client Side API - YouTube

And a link to blogs I have written about it can be found here: (+) The Client Side API in Sage CRM: A round up of articles. - Sage CRM Hints, Tips and Tricks - Sage CRM - Sage City Community 

That seems to work with standard entities for me now like this:

var CrmExample = CrmExample || {};

CrmExample.doit = function () {
var compField = crm.fields("vpos_text1");
var companyID = 10141;
var successCompany = function(crmRecord)
{
//crm.infoMessage(crmRecord.comp_name);
compField.title("Status: "+crmRecord.comp_status +"\n Type: "+crmRecord.comp_type);
document.EntryForm["vpos_text1"].value = crmRecord.comp_status;
}
crm.sdata({
entity: "company",
id: companyID,
success: successCompany
});}

Now I create a linked table to another database with allowed reading option by sdata.

When I try to get data from sdata like this 

http://xxcbx05/sdata/CRMj/sagecrm2/-/KagCRMPreise

I could not download the data.

With the SQL Server Profiler I can see that the SQL-Server gets the demand with:

exec sp_prepexec @p1 output,NULL,N'SELECT COUNT(*) FROM KagCRMPreise WITH (NOLOCK) WHERE null_Deleted IS NULL'

How can I get data from that linked table in my code?

Hi Nunzio

I think you may need to log a support request to establish why the request is failing with a linked database table exposed to SData. 

Hello, 

now I did it to request data from linked table.

I have to use a view with union like this:

 Building Cross Database Views for Reporting 

Now I have a problem to query my data.

When I use this I got a result:

var CrmExample = CrmExample || {};

CrmExample.doit = function () {
var compField = crm.fields("vpos_text1");
var ID = 99;
var art = 8;

var successCompany = function(crmRecord)
{
document.EntryForm["vpos_text1"].value = crmRecord.preis_preis;
}
crm.sdata({
entity: "vkagcrmpreisenew",
id: ID,
success: successCompany
});}

If I change the sdata parameter like this I get only "undefined".

var CrmExample = CrmExample || {};

CrmExample.doit = function () {
var compField = crm.fields("vpos_text1");
var ID = 99;
var art = 8;

var successCompany = function(crmRecord)
{
document.EntryForm["vpos_text1"].value = crmRecord.preis_preis;
}
crm.sdata({
entity: "vkagcrmpreisenew",
where: "preis_artnew eq "+art,
success: successCompany
});}

The field "preis_artnew" is an integer.

What is my fault here?

Thank you!

The CRM.sdata method uses the orginal RESTful API called SData.  You can use something like Postman to test the SData endpoints to see whether the call you are trying to make is allowed.

Yes Postman gives me a valid result.

I got it.

With a where clause the syntax must change to:

crmRecord[0].preis_preis