Thank you very much. I will need a drink to understand it :). But your example, is easier to understand than the other articles.

>Try after your code:
>
>

>declare @loop int = 0
>
>while @loop < 20
>  begin
>   set @loop = @loop + 1;
>insert into #myTest2
>(col1, col2test1)
>select 'Test insert into #myTest2', * from 
>(insert into #myTest1 (col1) output inserted.col2Test1 values ('Test Insert into #myTest1 iteration: ' + cast(@loop as varchar(10)))) s
>  end
>
>select * from #myTest1;
>select * from #myTest2;
>

>
>Also found this article which may be even simpler sample:
>
>https://www.codeproject.com/Articles/38871/Composable-DML-and-Merge-Statement-in-SQL-Server-2
>
>>Here is my "real" example on which I would like to learn this Composable SQL:
>>
>>

>>if object_id('tempdb..#myTest1', N'U') is not null drop table #myTest1;
>>if object_id('tempdb..#myTest2', N'U') is not null drop table #myTest2;
>>
>>declare @InsertOutput table
>>(
>>	new_ident int
>>)
>>create table #myTest1
>>(
>>	col1 varchar(50),
>>	col2Test1 int identity(1,1) not null
>>)
>>create table #myTest2
>>(
>>	col1 varchar(50),
>>	col2Test1 int
>>)
>>

>>
>>I would like to create a Insert into table #myTest1 and in the table #myTest2 in one statement, where the column col2Test1 of #myTest2 gets the value of the col2Test1 (Identity) of table #myTest1. (The column col2 of #myTest2 can get any dummy value, not important here).
>>
>>
>>Could you, please, show me how to do it?
>>
>>
>>>> Because, IMHO, the speed you gain with the Composable SQL vs two Inserts and output table is probably negligible (if anything).
>>>
>>>Speed is nothing compared to elegance :)
>>>
>>>Just think about a sub-query, you can say i.e.
>>>
>>>

select myData.* from (select * from myTable where myCondition) myData

>>>
>>>This was a terrible example of sub-query, completely unnecessary etc etc, but, it gives you the idea. When you put OUTPUT in your INSERT or UPDATE commands, is like it has an implicit sub-query and that is what you use. I am sure someone can explain it way better...