SQL Error: Cannot Insert Null (Fix + Examples)

Getting the "null value in column "column_name" violates not-null constraint" error in SQL? This guide explains what causes this error and how to fix it with practical examples.

What Causes This Error?

The cannot insert null error (23502) occurs when:

• Required column not included in INSERT statement
• Explicitly inserting NULL into a NOT NULL column
• Application passing null/undefined values
• Default value not set for required column

How to Fix It

1. Include all required columns in your INSERT statement.
2. Provide default values in your table schema: column_name TYPE NOT NULL DEFAULT value.
3. Validate data in your application before inserting.
4. Use COALESCE to provide fallback values.

Example: Wrong vs Correct

❌ Code That Causes the Error

INSERT INTO users (name) VALUES ('John');
-- Error: null value in column "email" violates not-null constraint

✅ Corrected Code

INSERT INTO users (name, email) VALUES ('John', 'john@example.com');
-- Correct: all required columns provided

Quick Checklist

• [ ] Verify column/table names are spelled correctly
• [ ] Check data types match expected values
• [ ] Review query syntax for missing keywords
• [ ] Ensure referenced tables/columns exist

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