SAS 9.4 Language Reference, 6th Edition

Note: For the CHANGE statement in PROC DATASETS, specifying GENNUM=0

refers to the entire generation group.

Using Passwords in a Generation Group

Passwords for versions in a generation group are maintained as follows:

• If you assign a password to the base version, the password is maintained in

subsequent historical versions. However, the password is not applied to any existing

historical versions.

• If you assign a password to a historical version, the password applies to that

individual data set only.

Understanding Integrity Constraints

Definition of Integrity Constraints

Integrity constraints are a set of data validation rules that you can specify in order to

restrict the data values that can be stored for a variable in a SAS data file. Integrity

constraints help you preserve the validity and consistency of your data. SAS enforces the

integrity constraints when the values associated with a variable are added, updated, or

deleted.

There are two categories of integrity constraints: general and referential.

CAUTION:

Do not use operating system tools when managing integrity constraints. This

can cause your data set to become damaged. Instead, use SAS tools such as the

DATASETS procedure or the SQL procedure.

General and Referential Integrity Constraints

General Integrity Constraints

General integrity constraints enable you to restrict the values of variables within a single

file. There are four types of general constraints:

check

limits the data values of variables to a specific set, range, or list of values. Check

constraints can also be used to ensure that the data values in one variable within an

observation are contingent on the data values of another variable in the same

observation.

not null

requires that a variable contain a data value. Null (missing) values are not allowed.

unique

requires that the specified variable or variables contain unique data values. A null

data value is allowed but is limited to a single instance.

primary key

requires that the specified variable or variables contain unique data values and that

null data values are not allowed. Only one primary key can exist in a data file.

Understanding Integrity Constraints 637