Remove rows when a value in one field is not found within another (nulls may occur):

[JoshuaElphee]

I have a large report (30x70K) where I need to perform the following action:

If the value in "Source if Appl." is not null, and the value of the cell is not found in "Proj", the field should be removed.  How do I make this occur?  All nulls should remain, but if "Source if appl." does not exist within "Proj" at least once, the entire row should be removed.

An example is found below, with column 4 being an example of the logic of whether the field remains or is removed.

ID	Proj.	Source if appl.	*Output intent
1	ABC	789	REMOVE (source if appl. not found in Proj)
2	123		Keep (no source if appl.)
3	DEF	123	Keep (source if appl found in proj.)
4	GHI		Keep (no source if appl.)
3	JKL	789	REMOVE (source if appl. not found in Proj)
5	MNO		Keep (no source if appl.)

[binuacs]

@JoshuaElphee Create a variable called flag and assign 1 or 0 based on your condition then filter out the one that you don't want

[Qiu]

@JoshuaElphee 
To reduce the computation, I first filter out the empty "Source if appl." then have to do an Append to locate relation between "the Proj."  and "Source if appl."

 

[JoshuaElphee]

The issue is that this is flagging 1 where there ARE comparable values in "proj."   row 3 should remain as the value is found in proj.