Indicates that a value is either unknown or undefined. NULL is not equivalent to a blank or empty string (for character columns) or 0 (for numerical columns).

Although you can write expressions that return nulls, any column that has the NOT NULL or PRIMARY KEY constraint will not accept nulls. Therefore, if the

Data Integration Service

tries to write a null value to a column with one of these constraints, the database will reject the row and the

Data Integration Service

will write it to the reject file. Be sure to consider nulls when you create transformations.

Functions can handle nulls differently. If you pass a null value to a function, it might return 0 or NULL, or it might ignore null values.