How to append data and remove duplicates in SAS with some constraints

[eagles_dare13]

I have a data set A which has values like:
1
1
2
3
3
4
5
5

(a.k.a some values are repeating)

I have another data set B with values like:

1
3
3
5
7
7
8

(a.k.a some values are repeating , some values are also in A, and some are new)

I want to create a dataset C such that it has every value from A and only those from B that are not in A.
So the final should look like:

1
1
2
3
3
4
5
5
7
7
8

So in short, duplicates within the same set are to be retained but if there is a duplicate across A and B, only retain the one from A. There is also a description column that says whether the value is in A or B.

How to do this?

[TomKari]

What about a case where A has

3

and B has

3

3

Should your result have one 3 or two 3's?

Also, do you need any other variables copied across, or only this one?

Tom

[eagles_dare13]

In that case, it should have one 3 only.

Also there are other variables, but they are descriptive, no decision is made based on those variables.

[Astounding]

It may be short but it's not that simple.

data want;

   from_a=0;

   merge a (in=from_a) b (in=from_b);

   by value;

   if first.value then do;

      if from_a and from_b then source='Both A and B';

      else if from_a then source='A only';

      else source='B only';

   end;

   retain source;

   if source='B only' then output;

   else if from_a then output;

run;

[slchen · Accepted solution]

DATA A;
INPUT X;
CARDS;
1
1
2
3
3
4
5
5
;
RUN;

DATA B;
INPUT X;
CARDS;
1
3
3
5
7
7
8
;
RUN;

PROC SQL;
  SELECT * FROM A
  UNION ALL
  SELECT * FROM B WHERE X NOT IN (SELECT * FROM A);
QUIT;

[eagles_dare13]

When SAS concatenates data sets with the union all statement and each data set has the exact same column names and column data types, will SAS use the ordering of the columns to figure out the corresponding columns or the actual names?

[Ksharp]

union all corr

[Ksharp]

proc sql;
create table want as
 select * from a
  union all
( select * from b
   except all
  select * from a)
;
run;

Xia Keshan