title: Counting occurrences of a value in a column of a table - postgresql
body: <p>I have a table with multiple columns:</p>
  
  <pre><code>table1 | column1 | column2 | column3 |
         |    x    |  ....   |   ....  |
         |    y    |  ....   |   ....  |
         |    x    |  ....   |   ....  |
  </code></pre>
  
  <p>How can I count the occurences of a value, for example x, in one of the columns, for example column1? Given table1 this would have to return me 2 (numbers of x present in column1).</p>