Hola @juan94, bienvenido a SAS Support Communities. Yo comprendo español un poco, pero hablamos ingles en este foro.
And...SAS syntax is based in English...
Your pseudocode (using a CASE statement) requires SQL. Is that how you intend to solve this? If so, the form of an SQL CASE statement is:
CASE (term | expression)
WHEN (compare-value | expression) THEN (result-value)
...
END as (target-variable)
So your example would be:
proc sql;
create table target as select *,
case t1.A
when 0 then "BUSCAR VALOR ANTERIOR"
else "default value"
end as new_value1,
case t1.MES
when 1 then t1.A
else t1.A
end as new_value2
from source_table;
quit;
Of course, second expression does not make sense, as it results in the same value whether for any condition of t1.MES (month). I'm not really sure what your objective is here -- but I might have missed something in my poor translation.
If you're new to SAS and using SQL syntax because that's what you're familiar with, I suggest trying with DATA step instead. That approach is much more flexible. Check out this tutorial, How to Write a Basic SAS Program. It's in English, but I think you can turn on captioning and that might help.
