title: What is SELECT 1=1 FROM TABLE?
body: <p>I found a query in MySql stored procedure where</p>
  
  <pre><code> SELECT 1=1 FROM ITEM_TABLE WHERE product_code = productCode;
  </code></pre>
  
  <p>What does this <code>1=1</code> means? is it means a <code>boolean</code> <code>true</code>?
  The outputs was few rows of <code>1</code>. 
  What does the output means? Do we really need to perform this type of check?</p>