CRUD Operations
Master the four fundamental database operations: Create, Read, Update, and Delete.
Inserting Data (CREATE)
Single Row Insert
INSERT INTO users (name, email, age)
VALUES ('John Doe', '[email protected]', 25);Multiple Row Insert
INSERT INTO users (name, email, age) VALUES
('Jane Smith', '[email protected]', 30),
('Bob Johnson', '[email protected]', 35),
('Alice Brown', '[email protected]', 28);Insert with Default Values
INSERT INTO users (name, email)
VALUES ('Charlie Wilson', '[email protected]');Querying Data (READ)
Basic SELECT
-- Select all columns
SELECT * FROM users;
-- Select specific columns
SELECT name, email FROM users;WHERE Clause (Filtering)
-- Basic condition
SELECT * FROM users WHERE age > 30;
-- Multiple conditions
SELECT * FROM users WHERE age > 25 AND name = 'John';
-- OR condition
SELECT * FROM users WHERE age < 25 OR age > 35;
-- Pattern matching
SELECT * FROM users WHERE name LIKE 'J%'; -- Starts with J
SELECT * FROM users WHERE email LIKE '%@example.com'; -- Ends withORDER BY (Sorting)
-- Sort by age ascending
SELECT * FROM users ORDER BY age;
-- Sort by name descending
SELECT * FROM users ORDER BY name DESC;
-- Sort by multiple columns
SELECT * FROM users ORDER BY age DESC, name ASC;LIMIT (Restricting Results)
-- Get first 5 users
SELECT * FROM users LIMIT 5;
-- Skip first 5, get next 5 (pagination)
SELECT * FROM users LIMIT 5 OFFSET 5;Updating Data (UPDATE)
Basic Update
UPDATE users
SET age = 26
WHERE name = 'John Doe';Update Multiple Fields
UPDATE users
SET age = 31, email = '[email protected]'
WHERE name = 'Jane Smith';Update with Condition
UPDATE users
SET age = age + 1
WHERE age < 30;Deleting Data (DELETE)
Delete Specific Rows
DELETE FROM users WHERE name = 'Bob Johnson';Delete with Condition
DELETE FROM users WHERE age > 40;⚠️ Warning: DELETE FROM users without a WHERE clause deletes all data!
Next Steps
Ready for more complex queries? Learn about Advanced Queries to use aggregate functions and grouping.
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