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Null Values

In most cases, columns in a table can contain null values. A null value means that the value for the column can be unknown or not applicable. For example, in the telephone directory example in Building a Relational Data Model, the anniv column of the name table can contain null values; if you do not know the person's anniversary, you do not specify it. Do not confuse null value with zero or a blank value. For example, the following statement inserts a row into the manufact table of the stores_demo database and specifies that the value for the lead_time column is null:

INSERT INTO manufact VALUES ('DRM', 'Drumm', NULL)
Dynamic Server

Collection columns cannot contain null elements. Creating and Using Extended Data Types in Dynamic Server describes collection data types.

End of Dynamic Server
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