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IS NULL Predicate

IS_NULL_predicate_ ::= expression IS [ NOT ] NULL

The IS NULL predicate allows comparing values with the NULL value. The predicate IS NOT NULL allows comparison with a non-empty value. The comparison "expression = NULL" is not allowed according to the SQL standard but is allowed in 602SQL.

The NULL value is identical to an empty string for string types.

Example:

Select invoices that are not yet paid.

SELECT *
FROM INVOICES
WHERE paid IS NULL
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