El Mar 28 Sep 2004 11:02, T E Schmitz escribió:
> Hello,
>
> Is it possible to set up a table CHECK, which ensures that column A is
> NOT NULL if column B = 'x' ?
CONSTRAINT constraint_name ] CHECK (expression)
CHECK (expression)
The CHECK clause specifies an expression producing a Boolean result which new
or updated rows must satisfy for an insert or update operation to succeed. A
check constraint specified as a column constraint should reference that
column's value only, while an expression appearing in a table constraint may
reference multiple columns.
So I would say that it should be:
CONSTRAINT somename CHECK (B <> 'x' OR A IS NOT NULL)
(use a logical table to build the correct logical expression)
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Martín Marqués | select 'mmarques' || '@' || 'unl.edu.ar'
Centro de Telematica | DBA, Programador, Administrador Universidad Nacional del Litoral
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