Column Ordering in the Data Step

[PeterClemmensen]

Hi All.

I like to control the column ordering of my data with a format statement immediately after the data statement as such

data test;
   format type origin;
   set sashelp.cars;
run;

, but I am yet to understand the logic as to why I do not get the same result when placing it after the set statement as

data test;
   set sashelp.cars;
   format type origin;
run;

 Can anyone enlighten me? 🙂

Regards.

[Kurt_Bremser · Accepted solution]

When the compiler builds the data step, it creates the PDV from the code it encounters. When a set statement is read, the data set is opened and the columns are put into the PDV, unless they are already there (at least in name). Therefore the ordering is set in example 1 by the format statement, and in example 2 by the ordering in sashelp.cars.

[PeterClemmensen]

Thank you, this makes sense.

[Shmuel]

Oreder of variables are defined by their first occurence in the datastep.

When you do SET before FORMAT, the order is taken from the input dataset.