How to fix ERROR 1406: Data too long for column in MySQL

The error message includes the column name. If it doesn't clearly show which column, check your INSERT/UPDATE statement:

-- This would fail on the 'email' column if it's too small
INSERT INTO users (id, name, email)
VALUES (1, 'John Doe', '[email protected]');

The error output shows: ERROR 1406: Data too long for column 'email' at row 1

Review the column definition to see its current maximum size.

Query the table schema to see the current column definition:

DESCRIBE users;
-- or
SHOW COLUMNS FROM users;

Look at the column causing the issue. For example, you might see:

email | varchar(50) | NO | UNI | NULL |

If you're trying to store email addresses, 50 characters is likely too small. Measure your actual data to determine the required size.

Use ALTER TABLE to expand the column:

ALTER TABLE users MODIFY COLUMN email varchar(255);

Choosing the right size:
- Email addresses: VARCHAR(255)
- Phone numbers: VARCHAR(20)
- URLs: VARCHAR(2083)
- Short text (names): VARCHAR(100-150)
- Long text (descriptions): TEXT or LONGTEXT

After altering the column, retry your INSERT/UPDATE operation.

If the data is genuinely variable in length and could exceed VARCHAR limits, use TEXT types:

-- For large text up to 64KB
ALTER TABLE articles MODIFY COLUMN content MEDIUMTEXT;

-- For very large text up to 4GB
ALTER TABLE logs MODIFY COLUMN message LONGTEXT;

Data type sizes:
- VARCHAR(N): max 65,535 bytes total (all columns combined)
- TEXT: 64 KB
- MEDIUMTEXT: 16 MB
- LONGTEXT: 4 GB

TEXT types are appropriate for blog posts, descriptions, and log entries.

To prevent this error in the future, add application-level validation:

JavaScript/Node.js:

const email = userData.email;
if (email.length > 255) {
  throw new Error('Email exceeds maximum length of 255 characters');
}

PHP:

$maxLength = 255;
if (strlen($email) > $maxLength) {
  throw new Exception('Email too long');
}

Python:

if len(email) > 255:
    raise ValueError('Email exceeds maximum length')

Validating data length in your application prevents bad data from ever reaching the database.

If the error occurs with a BIT column, the issue is usually incorrect value format. BIT columns expect binary literals, not quoted strings:

Incorrect (causes Error 1406):

UPDATE users SET is_active = '1' WHERE id = 1;  -- String '1' is 8 bits

Correct:

UPDATE users SET is_active = b'1' WHERE id = 1;  -- Binary literal is 1 bit
-- or
UPDATE users SET is_active = 1 WHERE id = 1;  -- Numeric value

The b prefix tells MySQL to interpret the value as a binary literal.