Re: CHECK col A not NULL if col B='x'

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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