Compare data from different data sets SAS

I have two tables table_A and table_B.

table_A

table_B

I want to compare the two datasets and if they don't match, then replace the data in table_B in table_A using SAS

data compare_test_2;
set table_A;
set table_B;

if table_A.Queue_nm = table_B.Queue_nm
and tableA.Cust_nm != table_B.Act_Cust_name
then do;
tableA.Cust_nm = table_B.Act_Cust_name
where table_A.Queue_nm = table_B.Queue_nm;
run;

I want the following output after the comparison and the data step

table_A

I get the following error

ERROR: DATA STEP Component Object failure.  Aborted during the COMPILATION phase.
ERROR 557-185: Variable table_A is not an object.

You can use SQL to update a table with values from a second table via a correlated subquery using a key variable.

Example:

proc sql;
  update table_a as outer
  set cust_nm = (select act_cust_nm from table_b as inner where inner.Queue_nm = outer.Queue_nm)
  where exists (select * from table_b as inner where inner.Queue_nm = outer.Queue_nm)
  ;

Another way to update a table in place is the MODIFY statement.

proc datasets nolist lib=work;
  modify table_a;
  create index Queue_nm;
quit;

data table_a;
  set table_b;
  modify table_a key=Queue_nm;
  cust_num = act_cust_num;
run;