RelaxedAliasChecking

V. Khorsun

(V.2.1) RelaxedAliasChecking is a new configuration parameter added to permit a slight relaxation of the Firebird 2.0.x restrictions on mixing relation aliases and table names in a query. For example, with RelaxedAliasChecking set to true (=1) in firebird.conf, the following query will succeed in Firebird 2.1, whereas it would fail in v.2.0.x, or in v.2.1 with the parameter set to its default of 0:

SELECT ATABLE.FIELD1, B.FIELD2
  FROM ATABLE A JOIN BTABLE B
  ON A.ID = BTABLE.ID

Caution

Understand that this is a temporary facility whose purpose is to provide some headspace for migrating systems using legacy code that exploited the tolerance of InterBase and older Firebird server versions to non-standard SQL usage.

Don't enable this parameter if you have no “offending” code in your applications or PSQL modules. It is not intended as an invitation to write sloppy code!
Regard it as a time-bomb. It will be permanently removed from a future release.