Агрегирующие функции

SELECT COUNT(*) "Employee Count" FROM employees WHERE manager_id = 122;

SELECT COUNT(*) "Employee Count", manager_id FROM employees GROUP BY manager_id ORDER BY manager_id;

SELECT COUNT(commission_pct) FROM employees;

Агрегирующие функции

SELECT COUNT(DISTINCT department_id) FROM employees;

SELECT MIN(salary), MAX(salary), AVG(salary) FROM employees WHERE manager_id = 122;

SELECT MIN(salary), MAX(salary), AVG(salary), job_id FROM employees GROUP BY job_id ORDER BY job_id;

Агрегирующие функции

SELECT department_id, MIN(salary), MAX (salary) FROM employees GROUP BY department_id HAVING MIN(salary) < 7000 ORDER BY MIN(salary);

HAVING – Where для функций

Управление данными

Вставки – INSERT

Обновление – UPDATE

Удаление - DELETE

Вставка

INSERT INTO employees VALUES (10, 'Enrique', 'Borges', 'enrique.borges', '555.111.2222', '01-AUG-05', 'AC_MGR', 9000, .1, 101, 110);

INSERT INTO employees (employee_id, last_name, email, hire_date, job_id, salary) VALUES (11, 'Doe', 'jane.doe', '31-AUG-05', 'SH_CLERK', 2400);

SELECT employee_id, last_name FROM employees WHERE employee_id = 10 or employee_id = 11;

Обновление

UPDATE employees SET salary = salary * 1.05 WHERE employee_id = 11;

SELECT salary FROM employees WHERE employee_id = 11;

Удаление

DELETE FROM employees WHERE employee_id = 10 OR employee_id = 11;

SELECT * FROM employees WHERE employee_id = 10 OR employee_id = 11;

Если вы случайно удалили не те строки, можно откатить изменения с помощью ROLLBACK

Выражения для управления транзакциями

COMMIT – применить

ROLLBACK - отменить

COMMIT

INSERT INTO employees (employee_id, last_name, email, hire_date, job_id, salary) VALUES (12, 'Doe', 'john.doe', '31-AUG-05', 'SH_CLERK', 2400);

UPDATE employees SET salary = salary*1.10 WHERE employee_id = 12;

COMMIT;

ROLLBACK

DELETE FROM employees WHERE last_name = 'Doe';

ROLLBACK;

SELECT * FROM employees WHERE last_name = 'Doe';

DDL

Язык описания данных. Используется для:

-создания таблиц

-изменения столбцов

-изменения ограничений

-переименования, удаления таблиц

-управления индексами, последовательностями и видами