7.19.6 NULL predicate

(1) Specification format

NULL-predicate ::= value-expression IS [NOT] NULL

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(2) Explanation of specification format

value-expression:

Specifies the column to be evaluated by the NULL predicate. It is specified in the form of a value expression. For details about value expressions, see 7.20 Value expression.

If a dynamic parameter is specified by itself, the assumed data type of the dynamic parameter will be VARCHAR(32000).

NOT:

If NOT is specified, rows that are not the null value will become the target of retrieval.

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(3) Evaluation of the predicate

The NULL predicate is TRUE for rows in which the value of the specified value expression is a null value. If NOT is specified, it is TRUE for rows in which the value of the specified value expression is not a null value.

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(4) Examples

Example 1

This example retrieves the customer IDs (USERID) from the customer table (USERSLIST) where the name (NAME) is the null value.

SELECT "USERID"
    FROM "USERSLIST"
        WHERE "NAME" IS NULL

The underlined portion indicates the NULL predicate.

Example 2

This example retrieves the customer IDs (USERID) from the customer table (USERSLIST) where the name (NAME) is not the null value.

SELECT "USERID"
    FROM "USERSLIST"
        WHERE "NAME" IS NOT NULL

The underlined portion indicates the NULL predicate.

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