Looking to append/create/insert new row to an existing table

[powerbiuser101]

I have 2 Tables, A & B. 

Table A is constantly changing on a weekly basis, whereas Table B will have records of date and sum. E.g. 

Table B

18.01.2018, 2

19.01.2018, 3

and so on, so we have a trend of a weekly value

I'm having a difficult time writing an IF statement in Advaned Editor to see if today's date already exist, then ignore, if today's datedoes not exist, then calculate sum in Table A and create a new row in Table B. 

I'm sure this could be resolved in the backend but it's what I have at the moment. 

[v-chuncz-msft · Accepted solution]

@powerbiuser101,

You may perform Group By operation first, then refer to the code in this thread.