In SAS, you can use a WHERE expression in the following
situations:

WHERE statement in both DATA and
PROC steps. For example, the following PRINT procedure includes a
WHERE statement so that only the observations where the year is greater
than 2001 are printed:
proc print data=employees;
where startdate > '01jan2001'd;
run;

WHERE= data set option. The following
PRINT procedure includes the WHERE= data set option:
proc print data=employees (where=(startdate > '01jan2001'd));
run;

WHERE clause in the SQL procedure,
SCL, and
SAS/IML software. For example, the following SQL procedure
includes a WHERE clause to select only the states where the murder
count is greater than seven:
proc sql;
select state from crime
where murder > 7;

WHERE command in windowing environments
like
SAS/FSP software:
where age > 15

SAS view (DATA step view,
SAS/ACCESS
view, PROC SQL view), stored with the definition. For example, the
following SQL procedure creates an SQL view named STAT from the data
file CRIME and defines a WHERE expression for the SQL view definition:
proc sql;
create view stat as
select * from crime
where murder > 7;
In some cases, you can
combine the methods that you use to specify a WHERE expression. That
is, you can use a WHERE statement as follows:

in conjunction with a WHERE= data
set option

along with the WHERE= data set
option in windowing procedures, and in conjunction with the WHERE
command

on a SAS view that has a stored
WHERE expression
For example, it might
be useful to combine methods when you merge data sets. That is, you
might want different criteria to apply to each data set when you create
a subset of data. However, when you combine methods to create a subset
of data, there are some restrictions. For example, in the DATA step,
if a WHERE statement and a WHERE= data set option apply to the same
data set, the data set option takes precedence. For details, see the
documentation for the method that you are using to specify a WHERE
expression.
Note: By default, a WHERE expression
does not evaluate added and modified observations. To specify whether
a WHERE expression should evaluate updates, you can specify the WHEREUP=
data set option. See the
WHEREUP= Data Set Option in SAS Data Set Options: Reference.