Примеры команд SQL в рамках урока #9

-- Агрегация данных в SQL с помощью функции COUNT
-- https://www.youtube.com/watch?v=8h7JGr9loFo

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-- Примеры команд SQL в рамках урока #9


SELECT * FROM EMPLOYEES;

SELECT COUNT(*) FROM EMPLOYEES;

SELECT COUNT(*) FROM EMPLOYEES
WHERE MANAGER_ID = 100;

SELECT JOB_ID, COUNT(*) FROM EMPLOYEES
GROUP BY JOB_ID;

SELECT JOB_ID, DEPARTMENT_ID, COUNT(*) FROM EMPLOYEES
GROUP BY JOB_ID, DEPARTMENT_ID;

SELECT JOB_ID, COUNT(DEPARTMENT_ID) FROM EMPLOYEES
GROUP BY JOB_ID;

SELECT COUNT(DEPARTMENT_ID), COUNT(*) FROM EMPLOYEES;

SELECT DEPARTMENT_ID, COUNT(*) FROM EMPLOYEES
GROUP BY DEPARTMENT_ID;