Working with SAS Data Sets |
Selecting Observations |
The WHERE clause conditionally selects observations, within the range specification, according to conditions given in the expression. The general form of the WHERE clause is as follows:
where
is a variable in the SAS data set.
is one of the following comparison operators:
less than
less than or equal to
equal to
greater than
greater than or equal to
not equal to
contains a given string
does not contain a given string
begins with a given string
sounds like or is spelled like a given string
is a literal value, a matrix name, or an expression in parentheses.
WHERE comparison arguments can be matrices. For the following operators, the WHERE clause succeeds if all the elements in the matrix satisfy the condition:
= |
? |
< |
<= |
> |
>= |
For the following operators, the WHERE clause succeeds if any of the elements in the matrix satisfy the condition:
= |
? |
=: |
=* |
Logical expressions can be specified within the WHERE clause by using the AND (&) and OR (|) operators. The general form is as follows:
clause&clause |
(for an AND clause) |
||
clause | clause |
(for an OR clause) |
where clause can be a comparison, a parenthesized clause, or a logical expression clause that is evaluated by using operator precedence.
For example, to list the names of all males in the data set CLASS, use the following statement:
> list all var{name} where(sex='M'); OBS NAME ------ ---------------------- 2 THOMAS 3 JAMES 5 JOHN 7 ROBERT 10 JEFFREY 12 HENRY 13 ALFRED 17 RONALD 18 WILLIAM 19 PHILIP
The WHERE comparison arguments can be matrices. In the following cases that use the =* operator, the comparison is made to each name to find a string that sounds like or is spelled like the given string or strings:
> n={name sex age}; > list all var n where(name=*{"ALFRED","CAROL","JUDY"}); OBS NAME SEX AGE ----- ---------------- -------- --------- 11 CAROL F 14.0000 13 ALFRED M 14.0000 14 JUDY F 14.0000 > list all var n where(name=*{"JON","JAN"}); OBS NAME SEX AGE ------ -------- -------- --------- 4 JANE F 12.0000 5 JOHN M 12.0000
To list AGE, HEIGHT, and WEIGHT for all students in their teens, use the following statement:
> list all var v where(age>12); OBS AGE HEIGHT WEIGHT ------ --------- --------- --------- 8 13.0000 56.5000 84.0000 9 13.0000 65.3000 98.0000 10 13.0000 62.5000 84.0000 11 14.0000 62.8000 102.5000 12 14.0000 63.5000 102.5000 13 14.0000 69.0000 112.5000 14 14.0000 64.3000 90.0000 15 15.0000 62.5000 112.5000 16 15.0000 66.5000 112.0000 17 15.0000 67.0000 133.0000 18 15.0000 66.5000 112.0000 19 16.0000 72.0000 150.0000
Note:In the WHERE clause, the expression on the left side refers to values of the data set variables, and the expression on the right side refers to matrix values. You cannot use comparisons that involve more than one data set variable in a single comparison; for example, you cannot use either of the following expressions:
list all where(height>weight); list all where(weight-height>0);
You could use the first statement if WEIGHT were a matrix name already defined rather than a variable in the SAS data set.
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