What does "%" in front of the variable in SAS pass-through exactly do / or means ?

Question

what exactly does "%" in pass through means ? I got this code from others, the code works fine but I just don't understand why would have to put % in front of the variables. If it's a %macro I don't see any macro code in library. Any explanation would help

proc sql;
  connect to odbc as d(datasrc=source);
  create table out as select * from connection to d
  (
    select
      t.id,t.rule_id,
      %application_id,
      t.date,
      %dpv, %dpvfn1, %dpvfn2, %dpvfn3,
      %AddressValid,%AddressValidMsg,%AddressType,    
      from &db2 t
      join &db3 dxs on t.id=dxs.id
 left join &db4 dxr on t.id=dxr.id
  );
  disconnect from d;
quit;

Answer 1

%MACRO X; VAR %MEND;

The above example is a definition of a macro.

In your question, all the columns with % are actually doing macro calls and replacing the calls with the values present in their macro definitions.For eg in ur select query...

select
      t.id,t.rule_id,
      %application_id,
      t.date,
      %dpv, %dpvfn1, %dpvfn2, %dpvfn3,
      %AddressValid,%AddressValidMsg,%AddressType,    
      from &db2 t
      join &db3 dxs on t.id=dxs.id
 left join &db4 dxr on t.id=dxr.id

%application_id,%dpv, %dpvfn1, %dpvfn2, %dpvfn3,%AddressValid,%AddressValidMsg,%AddressType

All these above macro calls will retrieve their corresponding definitions and replace them in the place of your select columns...