title: duplicate records from postgresql sql query
body: <p>Could anyone help me while running query in Postgresql. I'm getting a duplicate record.</p>
  <pre><code>SELECT a.id, b.parameter_id
  FROM products a
  LEFT JOIN products_parameters b ON b.product_id = a.id 
  WHERE a.category_id = 14 AND b.parameter_id = 22
  ORDER BY a.id
  </code></pre>
  <p>Result - duplicated rows:</p>
  <p><a href="https://i.stack.imgur.com/lT40O.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lT40O.png" alt="enter image description here" /></a></p>
  <p>My data from table products:</p>
  <pre><code>SELECT *
  FROM &quot;products&quot;
  WHERE &quot;id&quot; = '10'
  </code></pre>
  <p><a href="https://i.stack.imgur.com/Szixl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Szixl.png" alt="enter image description here" /></a></p>
  <p>My data from table products_parameters:</p>
  <pre><code>SELECT *
  FROM &quot;products_parameters&quot;
  WHERE &quot;product_id&quot; = '10'
  </code></pre>
  <p><a href="https://i.stack.imgur.com/5bNl0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5bNl0.png" alt="enter image description here" /></a></p>
  <p>What is wrong with my query?</p>