Yes, this sounds safer. 

I'm still curious what does [identity] do here?

property id as %Library.BigInt [ identity ];

is it only for "Object" access and not for SQL?

Ah, I see - 

  VALUES (saleId,companyId,productId,saleDate,saleAmountUSD)

Impressive indeed.

I'm curious how and if the approach work if the id name in csv is diffent of "id", e.g.."CompanyId"?

Wow. Thanks @Vitaliy Serdtsev !

This is impressive. 

So if I understand properly, LOAD DATA guesses somehow that id is the idkey and primarykey here?

&sql(LOAD DATA FROM FILE 'C:\data\companies.csv'
  INTO dc_onetomany.companies(id,name,industry,description,website)
  USING {"from":{"file":{"header":true}}})

if AllowIdentityInsert =1?
 

Thanks @Dan Pasco !

So this $system.SQL.SetIdentityInsert(1) is a system-wide setting, right?

It looks like there is an option to have it as a parameter for a class as well, like @Vitaliy Serdtsev shared above  

Thanks Dan!

I’m having these property in my class that allows inserting ID values via SQL:

Parameter ALLOWIDENTITYINSERT = 1;

is it what you are talking about?

define a property as IDENTITY

I’m defining an index on an property id:

Index COMPANIESPKEY1 On id [ IdKey, PrimaryKey, SqlName = COMPANIES_PKEY1, Unique ];

Is it enough?

USEEXTENTSET=1 is a default one now if you use DDL to create a class. Maybe for ObjectScript is a default as well.

Yes. But we can omit it here (set 0) for simplification. Still the issue is in IDs

Thanks, @Dan Pasco! My task is to understand how can I better deal in IRIS if I need to export data into csv that contains records that reference IDs.  So I be able to import this data back into IRIS (same or another) preserving all the existing linkages.

I posted an example app illustrating the task.

What I came up with so far is:

introducing my own index as IDKEY and PrimaryKey - that works well for importing data from csv containing IDs.

But if when I’m introducing new records then with ObjectScript it wants me to create new IDs. This is where I have questions - how do I do it in the best way. You say I can try %Counter instead of %BigInt?

Also published on OEX.

Thank you, @Herman Slagman 
This is how I'm tackling it now - setting it after importing data and using $I(myclassD) after.

THat's good to know, thank you @Robert Cemper !

I wish you use IRIS ID maintanence - but don't see how is it possible in this way. Published an example app - maybe you can make it. more details in the comment below.

Thank you @Matjaz Murko  , @Robert Cemper , @Vitaliy Serdtsev @Herman Slagman .

Of course, I'd love to let IRIS maintain IDs.

But I don't see if it is possible at all if I need to export data into csv that is connected to each other e.g. via IDs.

I've created an example app of a "SuperSystems Enterprise" software company, that produces software products of different kinds, and there are companies that exist and buy these products from time to time.

So there are 3 entities in such a given system: products, companies, and sales. And sales entity contains IDs of companies and products they purchased along with date and sum.

Here is the code - if you build it in docker it will load the data from 3 csv files in /data folder: companies.csv, products.csv and sales.csv into related classes.

Notice that companies.cls and products.cls in this case maintain their own ID not an IRIS one as I don't know the other way it can be performed in IRIS so that data on sales connecting products and companies can be imported accurately to the history before reflected in csv. Other than way I chose here.

I suggest anyone who is interested in an exercise to fork the project and change the iris classes structure, or IDs, or ways of loading data, so that still the history of sales will be accurate - in order to check it easie,r I've provided a unittest that will check the sums of sales for 103 and 104 companies as :

USER>zpm

ipm:USER>test dc-onetomany-case

What do you think? )

Id location is in place - and has Ids in the first index, like ^myclassD(1),^myclassD(2), etc.

But nothing is set in ^myclassD

Other parameters I have:

Property id As %Library.BigInt [ SqlColumnNumber = 14 ];

Parameter ALLOWIDENTITYINSERT = 1;

Index MYCLASSPKEY1 On id [ IdKey, PrimaryKey, SqlName = MYCLASSPKEY1, Unique ];

And I import IDs from the csv file.

so my 

set newid=$I(newid)

part uses $Increment

Yes, $I is the short of $Increment.

But from which global?

$Seq is a faster option of $Increment