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Constraints are used to limit the type of data that can go in table. Constraints can be specified when a table is created (with create table statement) or alter the table is created (with alter table statement).Integrity Constraints are very important tools which preserve the validity and consistency of your data. SAS enforces integrity constraints when values associated with a column are added, updated, deleted or any modifications in data.

Integrity constraints follows some set of rules:-

follow ANSI standards

cannot be defined for views

cannot be defined for historical versions of generation data set

There are 5 types of Constraints

  1. Check– Ensures that a specific set or range of values are the only values in a column. It can also check the validity of a value in one column based on a value in another column within the same row.
  2. Not Null—— Ensuring that column has non missing values in each row
  3. Unique—– Ensuring the uniqueness for value of column
  4. Primary Key–A table can have only one PRIMARY KEY. The PRIMARY KEY includes the attributes of the constraints NOT NULL and UNIQUE also linked with one row
  5. Foreign Key- This is linked with one or more rows The only acceptable values for a FOREIGN KEY are values of the PRIMARY KEY or missing values.

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