Presents your 
SQL SERVER E-NEWSLETTER for April 8, 2003

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USE COLUMNPROPERTY TO DETERMINE COLUMN CHARACTERISTICS

COLUMNPROPERTY is a statement that can help you determine the
characteristics of a particular column in a table. It looks like this:

COLUMNPROPERTY (id, column, property)

The arguments include the ID for the identifier of the table or
procedure, the column name, and the property being queried.

If a property is true, COLUMNPROPERTY returns an integer of one. If the
property returns false, COLUMNPROPERTY returns an integer of zero. If 
the input is invalid, COLUMNPROPERTY returns NULL.

Properties can include:

* AllowsNull
* IsComputed
* IsFulltextIndexed
* IsIdentity
* IsIndexable

In the following example, we'll use the pubs database to check if the
address column allows nulls:

Use Pubs
SELECT COLUMNPROPERTY ( OBJECT_ID('authors'), 'address', 'AllowsNull')

Since the address column does allow nulls, COLUMNPROPERTY returns a one.

Now we'll check the au_id column to determine if it allows nulls:

Use Pubs
SELECT COLUMNPROPERTY ( OBJECT_ID('authors'), 'au_id', 'AllowsNull')

Because au_id is set as the primary key column on this table, it does
not allow nulls and therefore returns an integer of zero.

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