Firebird 3.0

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select rdb$get_context('SYSTEM', 'ENGINE_VERSION') as version
     , rdb$character_set_name
from rdb$database;


VERSION
RDB$CHARACTER_SET_NAME


3.0.5
UTF8




CREATE TABLE employee
(
  id INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
  name VARCHAR (40) NOT NULL,
  title VARCHAR (25) NOT NULL,
  salary INTEGER NOT NULL,
  mgr_id INTEGER,
   
  CONSTRAINT sal_ng_mgr_ck CHECK (salary <= (SELECT salary FROM employee WHERE id = mgr_id)),
  CONSTRAINT sal_nl_emp_ck CHECK (salary >= (SELECT salary FROM employee WHERE mgr_id = id))
);


INSERT INTO employee (name, title, salary, mgr_id) VALUES (1, 'CEO', 100000, NULL);
1 rows affected

INSERT INTO employee (name, title, salary, mgr_id) VALUES (2, 'PM',   75000, 1);
1 rows affected

INSERT INTO employee (name, title, salary, mgr_id) VALUES (3, 'Dev',  50000, 2);
1 rows affected

SELECT * FROM employee;


ID
NAME
TITLE
SALARY
MGR_ID


1
1
CEO
100000
null

2
2
PM
75000
1

3
3
Dev
50000
2




INSERT INTO employee (name, title, salary, mgr_id) VALUES (4, 'Dev',  100000, 2);
1 rows affected

UPDATE employee SET salary = 10000 WHERE title = 'PM';
1 rows affected

SELECT  * FROM employee;


ID
NAME
TITLE
SALARY
MGR_ID


1
1
CEO
100000
null

2
2
PM
10000
1

3
3
Dev
50000
2

4
4
Dev
100000
2