How to prevent leaving an empty column in the database?

Use the NOT NULL constraint for this column when creating the table or altering an existing one.

When creating a table:

CREATE TABLE my_table (
    id INT PRIMARY KEY,
    name VARCHAR(255) NOT NULL, // Disallow NULL in the name column
    description TEXT
);

When altering an existing table:

ALTER TABLE my_table
MODIFY COLUMN name VARCHAR(255) NOT NULL;

This ensures that when inserting or updating data in this column, a value other than NULL must be provided.