How to merge two datasets with same ID and replace data on the blank

[ttqkroe]

ID	a	b	c	d
1		1	1	1
1		2	2	2
1	b	3	3	3
1		4	4	4

ID	a
1	c

The result should look like:

ID	a	b	c	d
1	c	1	1	1
1	c	2	2	2
1	b	3	3	3
1	c	4	4	4

Thanks!!!

[PeterClemmensen]

Does your second data set always have just one obs?

[ttqkroe]

Yes

[PeterClemmensen]

data one;
infile datalines dlm = ',' missover dsd;
input ID a $ b c d;
datalines;
1, ,1,1,1
1, ,2,2,2
1,b,3,3,3
1, ,4,4,4
;

 
data two;
input ID a $;
datalines;
1 c
;

data want;
   set one;
   z = 1;
   if a = "" then set two point = z; 
run;

[Kurt_Bremser · Accepted solution]

proc sql;
create table want as
  select
    t1.id,
    coalesce(t1.a,t2.a) as a,
    t1.b,
    t1.c,
    t1.d
  from have t1 left join upd t2
  on t1.id = t2.id
;
quit;