title: How to insert records from table to another without duplicate
body: <p>I have two tables t1 and t2. t1 has duplicated values. I need to insert all records from t1 to t2, but I don't want duplicates to occur in t2. I tried the following command which seems to me correct and no syntax error when I run it but the problem, it has 0 effect. No records from t1 inserted in t2.</p>
  
  <pre><code>insert into test.t2 (name2) 
  select name1 from test.t1 where NOT EXISTS (select name2 from test.t2);
  </code></pre>
  
  <p>Can anybody help ?</p>