Previous row value

[aramachandra]

Hi All

I am using the 8.0 version and have the following logic in the transformer to get the previous row value checked to raise unique sequence numbers

Mapping as viewed in transformer


<B>Derivation -------------------------> stage variable</B>

SOURCE COLUMN ------------------------------ > currentvalue

if currentvalue <> previousvalue then ----> mycounter
myycounter=mycounter+1 else mycounter
currentvalue ----------------------------------> previousvalue


But my previous and current columns are identifical when i view them in the next stage

Any ideas what is missing here


arvind

[aramachandra]

The source file is a simple text file with one column

COLUMN1

Test1
Test2
Test3


Arvind

[aramachandra]

Expected output is


1 Test1
2 Test2
3 Test3

[aramachandra]

I reviewed the other post for the similar situation and did not find anything in particular about version 8.

In general my logic is

currentvalue=source column
if previousvalue <> currentvalue then counter= counter+1 else counter
previousvalue=currentvalue

arvind

[chulett]

But my previous and current columns are identifical when i view them in the next stage

Of course, because your last stage variable derivation makes them the same and rightly so:

currentvalue ----------------------------------> previousvalue

Nothing looks obviously wrong to me, what output are you actually getting?

[aramachandra]

My output is

0 Test1
0 Test2
0 Test3

[chulett]

What do you have for the Initial Value of the counter and previousvalue stage variables? Hopefully something valid for the datatype and not just null/empty.

[aramachandra]

Initial value for the counter is 0
It is type integer

Initial value for the previous value is "none" and it is varchar 25

[chulett]

Set it to something you know won't ever match on the first comparison, say "?" for example. None means null so your <> check always fails.

[aramachandra]

Thanks it partly worked

As suggested I set the default to "$" for the previousvalue variable and "?" for the currentvalue variable

I added another output column with Y AND N indicator for the change

if PreviousValue <> CurrentValue then 'Y' else 'N'

This above statement seem to be recognizing the previousvalue and evaluating correctly

But then I have a simple statement like

if PreviousValue <> CurrentValue then myCounter = myCounter +1 else myCounter

with myCounter having a default value of 0

That seems to always evaluate to 0

[aramachandra]

Thanks it partly worked

As suggested I set the default to "$" for the previousvalue variable and "?" for the currentvalue variable

I added another output column with Y AND N indicator for the change

if PreviousValue <> CurrentValue then 'Y' else 'N'

This above statement seem to be recognizing the previousvalue and evaluating correctly

But then I have a simple statement like

if PreviousValue <> CurrentValue then myCounter = myCounter +1 else myCounter

with myCounter having a default value of 0

That seems to always evaluate to 0

[chulett]

But then I have a simple statement like

if PreviousValue <> CurrentValue then myCounter = myCounter +1 else myCounter

How 'like' that is it? Your syntax as posted is invalid if that's literally what you have in the derivation. It should be:

Code: Select all

if PreviousValue <> CurrentValue then myCounter+1 else myCounter

Expressions only, no direct assignments.

[aramachandra]

Thanks a lot and I am sure you had a laugh at the rudimentary mistake.

Nonetheless I greatly appreciate the help and we can consider this post closed and it worked

Regards
Arvind

[chulett]

No laughing here, just a learning opportunity. Sometimes it's hard to tell if something is wrong or right when someone says "I have something like this" in a job, your first inkling is to give them the benefit of the doubt and assume they've really got it correct. However, if we dig deeper and things still don't work we revisit those assumptions.

Glad you got it sorted out, please officially mark the post as Resolved - there's a button at the top of the screen for that.

[ray.wurlod]

I slept through most all of that!

(Time zone, not boredom. Excellent that it was systematically resolved.)