title: Why is this transaction schedule not serializable?
body: <p>I'm going over practice problems for my database course.</p>
  
  <p>We are given a transaction schedule:</p>
  
  <pre><code> T1            T2
   Read(A)
                 Write(B)
                 Commit
   Read(B)
   Write(B)
   Commit(B)
  </code></pre>
  
  <p>The book says that the above is not <strong>serial</strong>, but why?<br>
  It seems to me you could run T2 then run T1 and get the same result.</p>