Link a sequence with to an identity in hsqldb

问题:

In PostgreSql, one can define a sequence and use it as the primary key of a table. In HsqlDB, one can still accomplish creating an auto-increment identity column which doesn't link to any user defined sequence. Is it possible to use a user defined sequence as the generator of an auto-increment identity column in HsqlDB?

Sample sql in PostgreSql:

CREATE SEQUENCE seq_company_id START WITH 1;

CREATE TABLE company (
  id bigint PRIMARY KEY DEFAULT nextval('seq_company_id'),
  name varchar(128) NOT NULL CHECK (name <> '')
);

What's the equivalent in HsqlDB?

Thanks.

回答1:

In version 2.0, there is no direct feature for this. You can define a BEFORE INSERT trigger on the table to do this:

CREATE TABLE company ( id bigint PRIMARY KEY, name varchar(128) NOT NULL CHECK (name <> '') );

CREATE TRIGGER trigg BEFORE INSERT
ON company REFERENCING NEW ROW AS newrow 
FOR EACH ROW
SET newrow.id = NEXT VALUE FOR seq_company_id;

and insert without using any vlue for id

INSERT INTO company VALUES null, 'test'

Update for HSQLDB 2.1 and later: A feature has been added to support this.

CREATE SEQUENCE SEQU
CREATE TABLE company ( id bigint GENERATED BY DEFAULT AS SEQUENCE SEQU PRIMARY KEY, name varchar(128) NOT NULL CHECK (name <> '') );

See the Guide under CREATE TABLE http://hsqldb.org/doc/2.0/guide/databaseobjects-chapt.html#dbc_table_creation

In addition, 2.1 and later has a PostgreSQL compatibility mode in which it accepts the PostgreSQL CREATE TABLE statement that references the sequence in the DEFAULT clause and translates it to HSQLDB syntax.