mr-sazzad/2nd_day_with_postgreSQL

POSTGRE SQL
2️⃣ DAY
-- PAGINATION IN POSTGRE SQL

✅ SELECT * FROM Employee ORDER BY name DESC;   --DESCENDING ORDER

✅ SELECT * FROM Employee ORDER BY name DESC; --ASCENDING ORDER

✅ SELECT * FROM Employee ORDER BY name DESC LIMIT 1; -- LAST ITEM OR ONLY ONE ITEM FROM DESCENDING ORDER

✅ SELECT * FROM Employee ORDER BY name DESC LIMIT 1 OFFSET 5; -- 6TH ITEM FROM LAST


-- IN, NOT IN, BETWEEN, LIKE


✅ SELECT * FROM Employee WHERE empID IN (3, 5, 244)  -- GIVE ME JUST THOSE ITEMS WHICH CONTAIN THESE ID 🎈

✅ SELECT * FROM Employee WHERE empID NOT IN (1, 7, 2)  -- GIVE ME JUST THOSE ITEMS WHICH NOT CONTAIN THESE ID'S 🥗

✅ SELECT * FROM Employee WHERE empID BETWEEN 40 AND 50  -- GIVE ME JUST THOSE ITEMS WHICH BETWEEN 40 TO 50 🥱


-- STRING SEARCHING

✅ SELECT * FROM Employee WHERE name LIKE '%A%';  -- GIVE ME JUST THOSE ITEMS WHICH CONTAIN A EOES NOT METTERE WHERE (CASE SENSITIVE 🥵)

✅ SELECT * FROM Employee WHERE name LIKE 'A%';  -- GIVE ME JUST THOSE ITEMS WHICH ARE STARTED WITH CHARACTER A (CASE SENSITIVE 🥵)

✅ SELECT * FROM Employee WHERE name LIKE '%A';  -- GIVE ME JUST THOSE ITEMS WHICH ARE ENDS WITH CHARACTER A (CASE SENSITIVE 🥵)


-- SPECIFIC POSITION 👾

✅ SELECT * FROM Employee WHERE name LIKE '_A%';  -- GIVE ME JUST THOSE ITEMS THERE SECOND LETTER IS A (CASE SENSITIVE 🥵)

✅ SELECT * FROM Employee WHERE name LIKE '__A%';  -- GIVE ME JUST THOSE ITEMS THERE THIRED LETTER IS A (CASE SENSITIVE 🥵)

✅ SELECT * FROM Employee WHERE name LIKE '__A__';  -- GIVE ME JUST THOSE ITEMS THERE THIRED/MIDDLE  LETTER IS A (CASE SENSITIVE 🥵)

✅ SELECT * FROM Employee WHERE name LIKE 'A%O';  -- GIVE ME JUST THOSE ITEMS THERE FIRST LETTER IS A AND LAST LETTER IS O (CASE SENSITIVE 🥵)

-- GET ROWS THEIR DEFINED COLUMN IS NULL 🪹

✅ SELECT * FROM Employee WHERE name IS NULL;  -- GIVE ME JUST THOSE ITEMS THERE NAME VALUE IS NULL (CASE SENSITIVE 🥵) 1️⃣

✅ SELECT * FROM Employee WHERE name = NULL;  -- GIVE ME JUST THOSE ITEMS THERE NAME VALUE IS NULL (CASE SENSITIVE 🥵) 2️⃣


-- JOINING 🧑‍🤝‍🧑
-- 1️⃣ INNER JOIN IT WORKS ON TOWDAIMENTION

SELECT e.name, e.job_role, depertment_name    -- name and job_role FROM EMPLOYEE TABLE AND department_name FROM DEPARTMENT TABLE
 FROM Employee e  -- ALIAS
 INNER JOIN Department ON department_id = e.department_id   -- IT'S CALLED 'ON' CONDITION 🥗


-- AGGREGATE 🎈

1️⃣ SELECT AVG(salary) avarazeSalary FROM Employees   -- IS'S USED TO GETTING AVARAZE FROM A COLUMN AND avarazeSalary IS ALIAS 💡

2️⃣ SELECT AVG(salary) AS avarazeSalary FROM Employees   -- WE ALSO CAN USE AS FOR ALIASING 💡

3️⃣ SELECT MIN(salary) AS maxSalary FROM Employees   -- IT'S USED FOR GETTING MAX VALUE FROM A COLUMN 💡

4️⃣ SELECT MAX(salary) AS minSalary FROM Employees   -- IT'S USED FOR GETTING MIN VALUE FROM A COLUMN 💡

5️⃣ SELECT SUM(salary) AS totalSalary FROM Employees   -- IT'S USED FOR GETTING MIN VALUE FROM A COLUMN 💡


SELECT deptId AVG(salary) FROM employees GROUP BY  deptId  -- CREATE GROUP AND GET THERE SALARY 💡

SELECT * FROM EMPLOYEES e RIGHT JOIN departments d ON e.edptId = d.deptId  -- COMPLEX RIGHT JOIN MEANS RIGHT SIDE PRIORITY ✅

SELECT d.name
FROM EMPLOYEES e FULL JOIN departments d
ON e.edptId = d.deptId
GROUP BY d.name


SELECT d.name, AVG(salary)
FROM EMPLOYEES e FULL JOIN departments d
ON e.edptId = d.deptId
GROUP BY d.name


SELECT d.name, AVG(salary) , SUM(salary), MAX(salary), MIN(salary)
FROM EMPLOYEES e FULL JOIN departments d
ON e.edptId = d.deptId
GROUP BY d.name


SELECT d.name, AVG(salary) , SUM(salary), MAX(salary), MIN(salary)
FROM EMPLOYEES e FULL JOIN departments d
ON e.edptId = d.deptId
GROUP BY d.name
HAVING AVG(e.salary) > 20000
mr-sazzad / 2nd_day_with_postgreSQL

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