title: Update new column with value from jSON in the same row Postgres
body: <p>I had a table with 20k products. In this table I had a jSON column which contained several information about the product. I had to add a new column by a requirement of my boss which will contain the model name (which is inside the jSON).
  How can I do it?
  My table product has id = id of the product
  product_description = jSON with many details about the product
  and now a new column model_name which my boss wants available outside the jSON</p>
  
  <p>I usually did this query:</p>
  
  <pre><code>SELECT "productInfo"-&gt;'product_info'-&gt;&gt;'model_name' AS model_name FROM inv.product WHERE id = 1
  </code></pre>
  
  <p>to obtain the model_name</p>
  
  <p>I want to update all the products so the model_name is now in the new column model_name but i couldn't do it because i'm not familiar with mass updates.</p>
  
  <p>What i want to do in words is:</p>
  
  <pre><code>UPDATE inv.product SET model_name = ( QUERY TO SELECT THE VALUE OF THE model_name ) FOR EACH ROW
  </code></pre>