Tip #27 - Using Temp tables in Arrays

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[1] and CustTemp[2].

Let's write some C/AL Code with this.

We create a new record using CustTemp[1]. We then try a FINDFIRST on CustTemp[2]. Let's see what message we get.

How cool is this! The contents of the CustTemp[2] is the same as that of CustTemp[1].

So what can we do with this. Let's add some more code.

We add a new record to CustTemp[2] and filter on this value using CustTemp[1]. Then we show the value of Name and the number of records in CustTemp[2].

What does this give?

The CustTemp[1] now has the value of the Name we insterted in CustTemp[2]. CustTemp[2] ignores the filter we used in CustTemp[1].

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.

 

Cheers,

/Marq

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  • Hi Marc,

    for me, this is a bug, not a feature.

    It was only last thursday I accidently had to deal with this issue myself.

    In a report I needed variables to store many decimal values, 4 each record.

    I tried to solve that with temopary record variables with 4 dimensions each, hopefully to save too many variables.

    But as one dimension affects the other, this try was useless :-(

    I still do not see any sense in this ...

    PS: I could not have worked with a decimal array instead due to further reasons - so do not wonder ;-)

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