The following commands in isql cause the following output:
create table test(a int constraint integral unique);
show table test;
A INTEGER Nullable
Unique key (A)
isql CONSTRAINT.FDB -x
CREATE TABLE TEST (A INTEGER,
Notice the name "INTEGRAL" should be included in the definition because it was a user-defined, explicit name. However, isql (since it does the wrong internal logic) confuses it with the INTEG_* implicit constraint names and ignores it. Therefore, reconstructing the db from the script causes the creation of a constraint with an internal name and the loss of the original name.