How To Use an SQLite Database in a Flask Application for register / login get & post

Hello everyone,

I got a problem when I’m setting the register.html and would like to get the info to the database for login used. I’m struggling the login / register setup…

the problem i got from now:

sqlite3.OperationalError: table posts has no column named username

{% extends 'base.html' %}
  {% block content %}
  <form method="post">
  <br>
  <div class="bg-img">
      <div class="content">
          <header>Sign Up</header>
          <form action="#">
              <div class="field">
                  <span class="fa fa-user"></span>
                  <input type="text" name="username" required placeholder="Username" value="{{ request.form['Username'] }}">
              </div>
              <div class="field space">
                <span class="fa fa-user"></span>
                <input type="text" name="email" required placeholder="Email" value="{{ request.form['Email'] }}">
            </div>
            <div class="field space">
              <span class="fa fa-user"></span>
              <input type="text" name="phone" required placeholder="Phone" value="{{ request.form['Phone'] }}">
          </div>
              <div class="field space">
                  <span class="fa fa-lock"></span>
                  <input type="password" name="password" class="pass-key" required placeholder="Password" value="{{ request.form['Password'] }}">
                  <span class="show">SHOW</span>
              </div>
              <div class="field space">
                <span class="fa fa-lock"></span>
                <input type="password" class="pass-key" required placeholder="Confirm Password">
                <span class="show">SHOW</span>
            </div>
              <div class="field signup">
                  <input type="submit" value="Sign up">
              </div>
          </form>
          <div class="signup">
              Or Sign up with
          </div>
          <div class="links">
              <div class="facebook">
                  <i class="fab fa-facebook-f"><span>Facebook</span></i>
              </div>
              <div class="instagram">
                  <i class="fab fa-instagram"><span>Instagram</span></i>
              </div>
          </div>
      </div>
 </div>
</form>
  <script>
      const pass_field = document.querySelector('.pass-key');
      const showBtn = document.querySelector('.show');
      showBtn.addEventListener('click', function () {
          if (pass_field.type === "password") {
              pass_field.type = "text";
              showBtn.textContent = "HIDE";
              showBtn.style.color = "#3498db";
          } else {
              pass_field.type = "password";
              showBtn.textContent = "SHOW";
              showBtn.style.color = "#222";
          }
      });
  </script>

  {% endblock %}
  
  

@app.route('/register/', methods=('GET', 'POST'))
def register():
    if request.method == 'POST':
        username = request.form['username']
        email = request.form['email']
        phone = request.form['phone']
        if not username:
            flash('Usename is required!')
        elif not email:
            flash('Email is required!')
        elif not phone:
            flash('Phone is required!')
        else:
            conn = get_db_connection()
            conn.execute ('INSERT INTO posts (username, email, phone) VALUES (?, ?, ?)',
                          (username, email, phone))
            conn.commit()
            conn.close()
            return redirect(url_for('index'))
    return render_template('register.html')