New internal function to get the default value of the field
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Key: CORE-3583
URL: http://tracker.firebirdsql.org/browse/CORE-3583
Project: Firebird Core
Issue Type: New Feature
Components: Engine
Affects Versions: 2.5.0
Reporter: Ain Valtin
Priority: Minor
Add internal function to query the default value of a column:
DEFAULT_VALUE(table.field)
So one could write query like
SELECT ... WHERE DEFAULT_VALUE(field) <> field;
to get rows where value of certain field differs from the column's default
value.
It would be nice if there is DEFAULT context available in triggers so that one
could write
IF(NEW.Field IS DISTINCT FROM DEFAULT.Field)THEN
Feature should also be available in constraints, ie
CREATE TABLE TAB_Foo (
fieldA ...,
fieldB ...,
CONSTRAINT C_field_AB CHECK((fieldA <> DEFAULT)OR(fieldB <> DEFAULT))
);
to ensure that either fieldA or fieldB has a different value than default.
MySQL has such a function, called DEFAUL(), see
http://dev.mysql.com/doc/refman/5.5/en/miscellaneous-functions.html#function_default
The MySQL function raises error when the field doesn't have default defined, I
would prefer
that FB's implementation would return NULL, perhaps with addidional function
IS_DEFAULT_DEFINED() to check "the meaning of the NULL".
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