postgres=#
postgres=# CREATE TABLE employee
postgres-# (id integer PRIMARY KEY CHECK (id > 100),
postgres(# last_name text NOT NULL,
postgres(# first_name text);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "employee_pkey" for table "employee"
CREATE TABLE
postgres=#
postgres=# insert into employee values(1000, 'a', 'b');
INSERT 0 1
postgres=# insert into employee values(200, 'c', 'd');
INSERT 0 1
postgres=# insert into employee values(11, 'a', 'b');
ERROR: new row for relation "employee" violates check constraint "employee_id_check"
postgres=#
postgres=# select * from employee;
id | last_name | first_name
------+-----------+------------
1000 | a | b
200 | c | d
(2 rows)
postgres=#
postgres=# drop table employee;
DROP TABLE
postgres=#