snowflake_002_Snowflake SQL Basics – SELECT, INSERT, UPDATE, DELETE.md

Snowflake SQL Basics – SELECT, INSERT, UPDATE, DELETE

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Objectives

Learn how to use the four foundational DML (Data Manipulation Language) SQL commands in Snowflake:

• SELECT – Retrieve data from a table
• INSERT – Add new data into a table
• UPDATE – Modify existing records
• DELETE – Remove data from a table

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Prerequisites

Ensure the following before executing queries:

• You're connected to a Snowflake session.
• A database, schema, and warehouse are selected.
• Use this script to create a sample table:

CREATE OR REPLACE TABLE employees (
    id INT,
    first_name STRING,
    last_name STRING,
    department STRING,
    salary FLOAT
);

SELECT – Retrieve Data

-- Select all columns
SELECT * FROM employees;

-- Select specific columns
SELECT first_name, department FROM employees;

-- Filtering with WHERE clause
SELECT * FROM employees
WHERE department = 'Engineering';

-- Sorting
SELECT * FROM employees
ORDER BY salary DESC;

-- Limiting results
SELECT * FROM employees
LIMIT 5;

INSERT – Add New Rows

-- Insert a single row
INSERT INTO employees (id, first_name, last_name, department, salary)
VALUES (1, 'Alice', 'Johnson', 'Engineering', 95000);

-- Insert multiple rows
INSERT INTO employees (id, first_name, last_name, department, salary)
VALUES 
    (2, 'Bob', 'Smith', 'Marketing', 72000),
    (3, 'Carol', 'Williams', 'Engineering', 98000);

UPDATE – Modify Existing Data

-- Give all engineers a raise
UPDATE employees
SET salary = salary * 1.10
WHERE department = 'Engineering';

-- Change department of an employee
UPDATE employees
SET department = 'Product'
WHERE id = 2;

DELETE – Remove Rows

-- Delete a single employee
DELETE FROM employees
WHERE id = 3;

-- Delete all employees in Marketing
DELETE FROM employees
WHERE department = 'Marketing';