[resolved] tMap - update only if value is non-Null?

[soowork]

Is there a way, using tMap, to say that I only want to update a value in the output table if the matching input value is not NULL?
If the input value is non NULL, then I want to update the column. If the input value is NULL, I want to leave the existing value alone. This will vary from row to row.
I suspect this is quite simple, but I am struggling figuring it out. TIA.
Input
ID Value
1 cat
2 NULL
4 fish
Existing Table
1 kitten
2 snake
3 koala
4 turtle
5 dog

Result
1 cat
2 snake
3 koala
4 fish
5 dog

[Anonymous]

Hi Dorthy,
Could you please elaborate your case with an example with input and expected output values?
Best regards
Sabrina

[_AnonymousUser]

Here's my scenario.
I should take the first non null value.
I'm doing a lookup, where for one column i can have more than one values. 
Say for eg: (str1,str2,str3).-> In this case the value to be considered should be str1.
       case2: (null,str2,str3) -> In this case my value should be str2.
I need to handle this situation inside tmap where i should get the first non null value for that particular column.
Regards,
Dorthy