union all in data step

[Vijay77]

PROC SQL;
CREATE TABLE SL_1 AS
SELECT distinct A,AEC,'Patients ' AS VARIABLE, 1 AS GRP, COUNT(DISTINCT SUBJID) AS CNT
FROM A(WHERE=(FL='Y')) GROUP BY AEC
UNION ALL
SELECT distinct A,AEC,'Patients 2' AS VARIABLE, 2 AS GRP, COUNT(DISTINCT SUBJID) AS CNT
FROM A(WHERE=(FL='Y' AND FFL='N')) GROUP BY AEC
;quit;

How to write above code in Data step

[Tom]

In general you wouldn't combine those types of calculations with the step that combines the datasets into one data step.

To combine two datasets (aka UNION) just use the SET statement.

data want;
  set have1 have2;
run;

[yliu1234]

What if I have three tables that want to union?

[Reeza]

These are not three tables, it's one table with different summaries according to your posted code. Show the code for the three tables please. I suspect this could be simplified into 2 queries but need to see the full process.

DISTINCT isn't one that's great in SAS unless you have sorted data already, which may still be doable in a single data step.