Execute Macro inside SQL statement - sql

Question

The Situation:
I have a table mytable with two columns: tablename and tablefield:
|-----------|------------|
| tablename | tablefield |
|-----------|------------|
| table1 | id |
| table2 | date |
| table3 | etc |
|-----------|------------|
My core objective here is basically, make a Select for each of these tablenames, showing the MAX() value of its corresponding tablefield.
Proc SQL;
Select MAX(id) From table1;
Select MAX(date) From table2;
Select MAX(etc) From table3;
Quit;
ps: The solution have to pull the data from the table, so whether the table change its values, the solutions will make its changes also.
What I have tried:
From the most of my attempts, this is the most sofisticated and I believe the nearest from the solution:
proc sql;
create table table_associations (
memname varchar(255), dt_name varchar(255)
);
Insert Into table_associations
values ("table1", "id")
values ("table2", "date")
values ("table3", "etc");
quit;
%Macro Max(field, table);
Select MAX(&field.) From &table.;
%mend;
proc sql;
Select table, field, (%Max(field,table))
From LIB.table_associations
quit;
Creating the Macro, my intend is clear but, for this example, I should solve 2 problems:
Execute a macro inside an SQL Statement; And
Make the macro understand its String value parameter as an SQL command.

Answer 1

In a data step, you can use call execute to do what you're describing.
%Macro Max(field, table);
proc sql;
Select MAX(&field.) From &table.;
quit;
%mend;
data _null_;
set table_associations;
call execute('%MAX('||field||','||table||')');
run;

Answer 2

Macros are not necessary here as you can just generate the code using put statements in the data step:
filename gencode temp;
data _null_;
set table_associations end=eof;
file gencode;
if _n_=1 then put 'proc sql;';
put 'select max(' tablefield ') from ' tablename ';';
if eof then put 'quit;';
run;
%include gencode / source2;
filename gencode clear;
The code is written to the a temporary file named 'gencode'. You could make this file permanent if you want. _n_=1 and end=eof are used to print the statements before and after the queries. Finally, %include gencode runs the code and the source2 option prints the code to the log.