title: How to change substring in more than 1,000,000,000 records?
body: <p>I have a database table with columns <code>dbValues</code> and <code>dbKeys</code>. The <code>dbKeys</code> value is a string containing keys separated with <code>;</code>.</p>
  
  <pre><code>dbKeys 1: "name;age;color;...price"
  dbKeys 2: "city;street;age;...favourite_meal"
  ...
  </code></pre>
  
  <p><code>dbValues</code> has same formatting as <code>dbKeys</code> but contains values for this keys.</p>
  
  <pre><code>dbValues 1: "Peter;18;blue;...64"
  dbValues 2: "London;Main;40;...applepie"
  ...
  </code></pre>
  
  <p>There are more than <strong>1 000 000 000</strong> rows. I need to delete some keys and its values from all of the records where the key is, for example the <code>age</code> key, so the result would be:</p>
  
  <pre><code>dbKeys 1: "name;color;...price"
  dbKeys 2: "city;street;...favourite_meal"
  ...
  
  dbValues 1: "Peter;blue;...64"
  dbValues 2: "London;Main;...applepie"
  ...
  </code></pre>
  
  <p>Do you have any recommendation how to modify all the records with the specific key value in the <code>dbKeys</code> column in the most effective way? I prefer some SQL, or something in .NET / C#.</p>
  
  <p>My solution is to create for-cycle over all the records (or over every 1000 records) and change every record separately. But it doesn't look very effective to me. So I'm opened for any other suggestion.</p>