title: Deleting records from a table without primary key
body: <p>I need to delete some specific record from database table but table itself does not have primary key. So condition depends on other table. So what is the correct way to do that?</p>
  
  <pre><code>  delete from table_1 
      where exists 
           (select distinct tb.* 
            from table_1 tb, table_2 tb_2, table_3 tb_3
            where tb1.col = tb2.col
            and tb3.col = tb2.col
            and tb3.col_2= 10)
  </code></pre>
  
  <p>is that correct way to do that? Lets say table_1 has 4 columns and first two columns should be the criteria to remove.</p>