Firebird 2.1 Language Reference Update

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DDL statements
..
constraint pk_people primary key (id),
constraint uk_nickname unique (nickname) using index ix_nick
alter table people
add constraint fk_people_country
foreign key (country) references countries(code)
using desc index ix_people_country
Important
If you define a descending constraint-enforcing index on a primary or unique key, be sure to make any foreign
keys referencing it descending as well.
ALTER TABLE
Available in: DSQL, ESQL
ADD column: Context variables as defaults
Changed in: IB
Description: Any context variable that is assignment-compatible to the new column's datatype can be used as a
default. This was already the case in InterBase 6, but the Language Reference only mentioned USER.
Example:
alter table MyData
add MyDay date default current_date
ALTER COLUMN: DROP DEFAULT
Available in: DSQL
Added in: 2.0
Description: Firebird 2 adds the possibility to drop a column-level default. Once the default is dropped, there
will either be no default in place or – if the column's type is a DOMAIN with a default – the domain default
will resurface.
Syntax:
Example:
ALTER TABLE tablename ALTER [COLUMN] colname DROP DEFAULT
alter table Trees alter Girth drop default
An error is raised if you use DROP DEFAULT on a column that doesn't have a default or whose effective default
is domain-based.
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