title: SEL * vs SEL columns
body: <p>When i do a select * query where i join multiple tables am not getting any duplicates but when i select individual columns in the same query with same tables with same joins, am getting duplicate rows.</p>
  
  <p>E.g.,</p>
  
  <pre><code> SEL * FROM tablea a
  join tableb b
  on a.col1=b.col1
  join table c
  on b.col2=c.col2
  where XXXXX --&gt; no duplicates
  
  sel a.col1,b.col3,c.col4
  from tablea a
  join tableb b
  on a.col1=b.col1
  join table c
  on b.col2=c.col2
  where XXXXX --&gt; returns duplicates
  
  SEL * FROM tablea a
  join tableb b
  on a.col1=b.col1
  join table c
  on b.col2=c.col2
  where XXXXX --&gt; no duplicates
  
  sel a.col1,b.col3,c.col4
  from tablea a
  join tableb b
  on a.col1=b.col1
  join table c
  on b.col2=c.col2
  where XXXXX --&gt; returns duplicates
  </code></pre>