title: How to add a column default?
body: <p>I created a Postgres DB which contains 5 tables. Then I realized that the column <code>student.student_id</code> lacks a column default to generate an <em>UUID</em>:</p>
  <pre><code>CREATE TABLE student (
       student_id UUID PRIMARY KEY,
       first_name VARCHAR(100) NOT NULL,
       last_name varchar(100) NOT NULL,
       date_of_birth Date NOT NULL
  )
  </code></pre>
  <p>Knowing that some tables are linked to the <code>student</code> table, how can I add to the function as column default for <code>student_id</code> so that the result will be:</p>
  <pre><code>     student_id UUID PRIMARY KEY DEFAULT uuid_generate_v4()
  </code></pre>