how to replace a empty data with null

Hello,

I have an input data which looks like this:

Code	value
21	1324
Z4	3564
L3	6798
34	9867
LP	5423
98	4459
2T1	1121
11	4112

I output should look like this (exactly in this order):

Code	Value
2T1	1121
Z4	3564
25	Null
11	4112
98	4459
16	Null
21	1324
L3	6798
34	9867

Input file can change time to time and might always contain the same codes while the output format is always the same.

I want the values to be filled in output file when the code exists in the input and all the codes that do not exist in input file should be Null or blank.

I have used the filter tool but it returnes a empty data if the criteria is not fullfilled, for example " [Code]= "16" " within a filter will return an empty data considering that code 16 does not exist in the input file.