Subquery Using Exists and Not-Exists Function: A Deep Dive into Snowflake SQL Functions
In this comprehensive tutorial, we explore the intricate nuances of Snowflake SQL functions, focusing specifically on exits and non-exits. Whether you're a beginner or an experienced SQL user, this video will provide you with invaluable insights into leveraging these functions effectively in your Snowflake data warehouse environment. Join us as we dissect the intricacies of exits and non-exits, uncovering their practical applications and optimizing your SQL queries for maximum efficiency. Don't miss out on this essential guide to mastering Snowflake SQL functions!
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SQL query
-- Exits and NOT EXITS
/*
In Snowflake, the EXISTS and NOT EXISTS functions are used to check for the existence or non-existence of rows in a subquery.
*/
-- Create the employees table
CREATE OR REPLACE TABLE employees (
employee_id INT,
employee_name VARCHAR(100),
department_id INT
);
-- Insert sample data into the employees table
INSERT INTO employees (employee_id, employee_name, department_id)
VALUES
(1, 'John Doe', 1),
(2, 'Jane Smith', 2),
(3, 'Alice Johnson', 1),
(4, 'Bob Brown', 3),
(5, 'Charlie Davis', 2),
(6, 'Eva White', 4);
SELECT * FROM employees;
-- Create the departments table
CREATE OR REPLACE TABLE departments (
department_id INT,
department_name VARCHAR(100)
);
-- Insert sample data into the departments table
INSERT INTO departments (department_id, department_name)
VALUES
(1, 'Sales'),
(2, 'Marketing'),
(3, 'Finance'),
(4, 'Engineering');
--Using EXISTS:
/*
Suppose you have two tables:
employees and departments.
You want to retrieve all departments that have at least one employee assigned to them.
*/
SELECT *
FROM departments d
WHERE EXISTS (
SELECT 1
FROM employees e
WHERE e.department_id = d.department_id
);
select * from departments d
where department_id in (select department_id from employees e);
-- Using NOT EXISTS:
--display all the departments that have no employees
SELECT *
FROM departments d
WHERE NOT EXISTS (
SELECT 1
FROM employees e
WHERE e.department_id = d.department_id
);
select * from departments d
where department_id not in (select department_id from employees e);
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