The main thing to watch out for is the usage of the <1,-1>
code for accessing/updating a list. When you insert a NULL using <1,-1>,
it doesn’t really do anything.
In this case, we had three lists that were being used like
an association, trying to be retrieve data from a record:
*Stores each field we care about from STUDENT.ACAD.CRED
record in lists. The intention is that these lists are associated.
FOR_EACH REFERENCED SECONDARY PST.STUDENT.ACAD.CRED
XL.STC.CMPL.CRED<1,-1> =
V.STC.CMPL.CRED
XL.STC.STATUS<1,-1> =
VL.STC.STATUS<1,1>
XL.STC.END.DATE<1,-1> = V.STC.END.DATE
END_EACH PST.STUDENT.ACAD.CRED
The issue arises when you consider how assigning NULLs work
in UniData. Since a NULL, in Envision, is not actually a character but an empty
string, assigning a null to a list doesn’t actually update the list, so when we
hit a NULL value in the assignment the positions of the three lists went wrong.
If our starting data was like this:
Record #1:
V.STC.CMPL.CRED = NULL
VL.STC.STATUS<1,1> = ‘N’
V.STC.END.DATE = ‘7/11/2014’
Record #2:
V.STC.CMPL.CRED = ‘3.00’
VL.STC.STATUS<1,1> = ‘N’
V.STC.END.DATE = ‘7/12/2014’
Our ending lists would look like this, based on our code
above:
STC.CMPL.CRED
|
STC.STATUS
|
STC.END.DATE
|
|
1
|
3.00
|
N
|
7/11/2014
|
2
|
NULL
|
N
|
7/12/2014
|
In record 1, V.STC.CMPL.CRED was NULL, so it actually did
not create a delimiter in the XL.STC.CMPL.CRED in position 1; we merely set the
tail of the list equal to NULL, so it didn’t actually do anything. The
next record then sticks ‘3.00’ into the tail of the list, which is in position
1. Since position 2 is never set, our three lists are going to look like:
XL.STC.COMPLE.CRED = ‘3.00’
XL.STC.STATUS = ‘N’:@VM:’N’
XL.STC.END.DATE = ‘7/11/2014’:@VM:’
7/12/2014’
Example of the issue using <1,-1>:
XL.LIST<1,-1>
= ‘’
XL.LIST<1,-1>
= ‘’
XL.LIST<1,-1>
= ‘’
XL.LIST<1,-1>
= ‘’
XL.LIST<1,-1>
= ‘’
XL.LIST<1,-1>
= ‘TEST’
In this case, XL.LIST is now equal to ‘TEST’ with no
delimiters. In order to make this work, what you actually need to do is
explicitely define the positions:
XL.LIST<1,1>
= ‘’
XL.LIST<1,2>
= ‘’
XL.LIST<1,3>
= ‘’
XL.LIST<1,4>
= ‘’
XL.LIST<1,5>
= ‘’
XL.LIST<1,6>
= ‘TEST’
Now XL.LIST is equal to ‘’:@VM:’’:@VM:’’:@VM:’’:@VM:’’:@VM:’TEST’
with @VM as the delimiter.
In order to fix the original code, I replaced
FOR_EACH REFERENCED SECONDARY PST.STUDENT.ACAD.CRED
XL.STC.CMPL.CRED<1,-1> =
V.STC.CMPL.CRED
XL.STC.STATUS<1,-1> =
VL.STC.STATUS<1,1>
XL.STC.END.DATE<1,-1> = V.STC.END.DATE
END_EACH PST.STUDENT.ACAD.CRED
With
X.ACAD.COUNTER = ‘1’
FOR_EACH REFERENCED SECONDARY PST.STUDENT.ACAD.CRED
XL.STC.CMPL.CRED<1,X.ACAD.COUNTER> = V.STC.CMPL.CRED
XL.STC.STATUS<1,X.ACAD.COUNTER >
= VL.STC.STATUS<1,1>
XL.STC.END.DATE<1,X.ACAD.COUNTER> = V.STC.END.DATE
X.ACAD.COUNTER = X.ACAD.COUNTER + 1
END_EACH PST.STUDENT.ACAD.CRED
* Cited from Trevyn Bowden.
