Expansion of Null-predicate

The null-predicate tests whether a value in a column is null.
idmscu19
The null-predicate tests whether a value in a column is null.
Syntax
Expansion of null-predicate
►►── 
value-expression
 ── IS ─┬───────┬─ NULL ─────────────────────────────────►◄                              └─ NOT ─┘
Parameters
  • value-expression
    Specifies the value to be tested.
  • IS NULL
    Directs CA IDMS to test for the presence of a null value.
  • NOT
    Reverses the test. NOT directs CA IDMS to test for the presence of a non-null value.
Usage
Truth Value of a NULL Predicate without NOT
The result of a NULL predicate that does
not
include NOT is:
  • True when the value being tested is null
  • False when the value being tested is not null
Truth Value of a NULL Predicate with NOT
The result of a NULL predicate that includes NOT is:
  • True when the value being tested is not null
  • False when the value being tested is null
Example
As the Search Condition in a WHERE Parameter
The following SELECT statement identifies employees for whom no telephone number has been stored in the database:
select emp_id    from employee    where phone is null;
For more information about search conditions, see Expansion of Search-condition.