Eloquent error: Cannot add a NOT NULL column with default value NULL

The Problem

When working with Laravel’s Eloquent ORM to handle Database interactions, developers might sometimes run into this particular error message: Cannot add a NOT NULL column with default value NULL. This error typically arises when attempting to add a new column to an existing table without providing a valid default value. Below are some solutions to overcome this issue.

Solution 1: Add Column with Default Value

One reason for this error is the omission of a default value for a column that does not allow NULL values. In SQL, if you do not specify a default value for a NOT NULL column, the database engine assumes it to be NULL, which then results in the error.

• Step 1: Use the default() method provided by Eloquent’s Schema Builder to give a default value when adding the column.
• Step 2: Run the migration.

Example:

Schema::table('users', function (Blueprint $table) {
    $table->string('new_column')->default('default_value')->nullable(false);
});

Output:

Migration ran successfully.

Notes

This is a clean approach ensuring that the database’s integrity isn’t compromised, and it avoids potential issues with missing data for newly added columns.

Solution 2: Add Nullable Column and Update Values

Another solution is to add the column as nullable, populate it with the desired data, and then change the column to NOT NULL:

• Step 1: Add the column as nullable.
• Step 2: Update the new column for each row as needed.
• Step 3: Alter the column to NOT NULL once all rows have been updated.
• Step 4: Run migrations again to apply changes.

Example:

Schema::table('users', function (Blueprint $table) {
    $table->string('new_column')->nullable();
});

// Pretend we have a User model and we set 'default_value' for new_column.
User::query()->each(function ($user) {
    $user->new_column = 'default_value';
    $user->save();
});

Schema::table('users', function (Blueprint $table) {
    $table->string('new_column')->nullable(false)->change();
});

Output:

Migration and update ran successfully

Notes

This approach is helpful when you need to compute default values based on the existing data and cannot simply assign a static default value. It’s a bit more involved but provides flexibility.