topic Re: what does null (missing variables) stand for? in SAS Programming

what does null (missing variables) stand for?

ResoluteCarbon — Tue, 30 Mar 2021 21:59:59 GMT

Hi all,

I am wondering what does Null stand for? Does it can be used to replace missing in both character and numeric data.

The background is that, the missing variable in character column is represented as " " while it is "." in numeric column.

What I mean is, for the example above, whether we can wrote ?

where Age =null;

/*or*/

where Name = null;

Thank you!

Re: what does null (missing variables) stand for?

Tom — Tue, 30 Mar 2021 22:11:39 GMT

The keyword NULL has meaning in SQL. It can be used to replace either numeric missing (the period) or all blank character string you would normally use in regular SAS code.

Because SAS consolidated the code/logic used to evaluate WHERE statements with the way they process SQL code you can use it in WHERE statements outside of PROC SQL.

522   data x;
523    set sashelp.class;
524    where age is null;
525   run;

NOTE: There were 0 observations read from the data set SASHELP.CLASS.
      WHERE age is null;
NOTE: The data set WORK.X has 0 observations and 5 variables.

But if you use the string NULL in regular SAS statement it is just a reference to a variable with that name.

530   data z;
531    set sashelp.class;
532    if age = null ;
533   run;

NOTE: Variable null is uninitialized.

Re: what does null (missing variables) stand for?

mkeintz — Tue, 30 Mar 2021 22:11:41 GMT

@ResoluteCarbon wrote:

Hi all,

I am wondering what does Null stand for? Does it can be used to replace missing in both character and numeric data.

The background is that, the missing variable in character column is represented as " " while it is "." in numeric column.

What I mean is, for the example above, whether we can wrote ?
where Age =null;

/*or*/

where Name = null;
Thank you!

NULL does NOT mean missing - it means a variable named "null".

Try

where missing(varname);

The MISSING function works on both numeric and character variables.