title: Postgresql with java: query produced no result after insert
body: <p>I write a little program to admin my video collection.</p>
  
  <pre><code>/*
  insert new data set into the table
  */
  int next = 0;
  rs = st.executeQuery("Select max(category_id) from category;");
  if (rs.next()) {
      next = rs.getInt(1) + 1;
      System.out.println(next);
  }
  String query = "INSERT INTO category VALUES (" + next + ", 'Mystics', now());";
  rs = st.executeQuery(query);
  //on this place is the exception thrown
  // this will not execute anymore
  rs = st.executeQuery("DELETE FROM category WHERE name = 'Mystics';"); 
  </code></pre>
  
  <p>The program can select on tables, make joins but insert make trouble.
  I try to insert some new data in my table (see Java-code). After the second test the output show me that the data was inserted. But after Insert was an exception thrown.
  1 &amp; 2 are the tests from yesterday and today. (3) was inserted but not selected yet.</p>
  
  <pre><code>1   Mystics 2015-07-05
  2   Mystics 2015-07-06
  3
  org.postgresql.util.PSQLException: query produced no result.
  at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:287)
  at postgre_java.Zetcode.main(Zetcode.java:55)
  </code></pre>
  
  <p>do you have some advises for me?</p>