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Joins.sql
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Joins.sql
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SELECT *
FROM employee_demographics;
SELECT *
FROM employee_salary;
#JOINS
#INNER JOIN -- returns the data of the common row
SELECT
* FROM employee_demographics emp_d
INNER JOIN employee_salary emp_s
ON emp_d.employee_id = emp_s.employee_id;
#OUTER JOIN
#LEFT JOIN -- returns all the row of the left table and only the common row from the right table
SELECT *
FROM employee_demographics demo
LEFT JOIN employee_salary sal
ON demo.employee_id = sal.employee_id;
#RIGHT JOIN -- returns all the row of the RIGHT table and only the common row from the LEFT table
SELECT *
FROM employee_demographics demo
RIGHT JOIN employee_salary sal
ON demo.employee_id = sal.employee_id;
#SELF JOIN
SELECT sal1.employee_id AS emp_santa,
sal1.first_name AS first_name_santa,
sal1.last_name AS last_name_santa,
sal2.employee_id AS empid,
sal2.first_name AS firstname,
sal2.last_name AS lastname
FROM employee_salary sal1
JOIN employee_salary sal2
ON sal1.employee_id +1 = sal2.employee_id;
#Joining multiple tables
SELECT *
FROM employee_demographics DEMO
INNER JOIN employee_salary SAL
ON DEMO.employee_id = SAL.employee_id
INNER JOIN parks_departments PARK
ON SAL.dept_id = PARK.department_id;