Примеры команд SQL в рамках урока #11

-- Оператор DISTINCT. Подсчет уникальных записей и удаление дублей
-- https://www.youtube.com/watch?v=tPv5ZSzPWc4

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-- Примеры команд SQL в рамках урока #11


SELECT COUNT(JOB_ID)
FROM EMPLOYEES;


SELECT COUNT(JOB_ID), COUNT(DISTINCT JOB_ID)
FROM EMPLOYEES;


SELECT DISTINCT JOB_ID
FROM EMPLOYEES;


SELECT DISTINCT JOB_ID, MANAGER_ID, DEPARTMENT_ID
FROM EMPLOYEES;


SELECT DISTINCT JOB_ID, MANAGER_ID, DEPARTMENT_ID
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 50;


SELECT DISTINCT JOB_ID, MANAGER_ID, DEPARTMENT_ID
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 50
ORDER BY JOB_ID, MANAGER_ID;


SELECT COUNT(DISTINCT JOB_ID, MANAGER_ID, DEPARTMENT_ID)
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 50;


SELECT COUNT(DISTINCT JOB_ID || MANAGER_ID || DEPARTMENT_ID)
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 50;


SELECT DISTINCT JOB_ID || MANAGER_ID || DEPARTMENT_ID
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 50;