I'll be honest, I found this out by accident lately but I want to share it anyway. Since it took me almost 15 years to find, it might not be know to some others.
As many of you know, using temporary tables in Microsoft Dynamics NAV is a very powerfull feature. We can use it to buffer data, to simulate SELECT DISTINCT etc. And they are free.
Using temporary tables becomes even more powerfull when adding an array to it. Let's see this in an example.
We'll create a new codeunit with a variable CustTemp that has two dimensions.
So now we can use CustTemp and CustTemp.
Let's write some C/AL Code with this.
We create a new record using CustTemp. We then try a FINDFIRST on CustTemp. Let's see what message we get.
How cool is this! The contents of the CustTemp is the same as that of CustTemp.
So what can we do with this. Let's add some more code.
We add a new record to CustTemp and filter on this value using CustTemp. Then we show the value of Name and the number of records in CustTemp.
What does this give?
The CustTemp now has the value of the Name we insterted in CustTemp. CustTemp ignores the filter we used in CustTemp.
Ok Mark, great stuff but what can I do with this?
Microsoft uses this in at least two places in the standard Navision product.
The fist place is the UpdInvPostingBuffer() function in Codeunits 80 and 90. This temporary buffer variable has two dimensions which are used to combine a select distinct with a total of the values.
The second place is the Inventory Profile Offsetting Codeunit (99000854) in Navision Manufacturing. In this codeunit supply and demand is created in the InventoryProfile table.
That was my first reaction as wel. Using this for a report and asuming it was a bug.
Later, going though these codeunits I realised that it is used by Microsoft. Codeunit 80 and 90 are very old and the design of the buffer has never changed much.
Therefore I assume this is by design.
However, I will discuss this with the product team. I will send them an email. I will also travel to the MDCC in a few weeks so I can ask them directly. :)