How to fix ERROR 1048: Column cannot be null in MySQL

-- Example error message: Column 'email' cannot be null
-- This tells you the 'email' column is the problem

-- WRONG: Missing 'email' value
INSERT INTO users (username, email) VALUES ('john', NULL);

-- CORRECT: Provide a valid email
INSERT INTO users (username, email) VALUES ('john', '[email protected]');

-- WRONG: Updating to NULL
UPDATE users SET email = NULL WHERE id = 1;

-- CORRECT: Update with a valid value
UPDATE users SET email = '[email protected]' WHERE id = 1;

// Node.js / Express example
app.post('/users', (req, res) => {
  const { username, email } = req.body;
  
  // Validate required fields
  if (!email || email.trim() === '") {
    return res.status(400).json({ error: 'Email is required' });
  }
  
  // Now safe to insert
  const result = await db.query(
    'INSERT INTO users (username, email) VALUES (?, ?)',
    [username, email]
  );
});

-- View table structure
DESCRIBE users;
-- or
SHOW COLUMNS FROM users;
-- or in more detail
SHOW CREATE TABLE users\G

-- Modify existing column to add default
ALTER TABLE users MODIFY COLUMN status VARCHAR(50) NOT NULL DEFAULT 'active';

-- When creating new table
CREATE TABLE users (
  id INT PRIMARY KEY AUTO_INCREMENT,
  username VARCHAR(100) NOT NULL,
  email VARCHAR(100) NOT NULL,
  status VARCHAR(50) NOT NULL DEFAULT 'active',
  created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);

-- Allow NULL values in this column
ALTER TABLE users MODIFY COLUMN phone_number VARCHAR(20) NULL;

-- Now these operations are valid
INSERT INTO users (username, email, phone_number) VALUES ('john', '[email protected]', NULL);
UPDATE users SET phone_number = NULL WHERE id = 1;