title: Oracle join tables using string functions
body: <p>I have to join table <code>CAMPAIGN</code> and <code>WF_ACTIVITY</code> such that <code>CAMPAIGN.CAMPAIGN_KEY = WF_ACTIVITY.PARAMETERS='CAMPAIGN_KEY='</code>.The <code>WF_ACTIVITY</code> table has Parameters column which contains value for example as :</p>
  
  <pre><code>CAMPAIGN_KEY=ROAMING_DATA_FLAT
  STEP_KEY=START_COLLECTION
  PARAM_KEY=BYPASS_PROVISIONING
  </code></pre>
  
  <p>I have to take only the value which has <code>'CAMPAIGN_KEY='</code> string from Parameters column and join it with <code>CAMPAIGN_KEY</code> column value from the <code>CAMPAIGN</code> table.I really dont know which string functions i can use or how do i trim the string part from Parameters columns which has value <code>'CAMPAIGN_KEY='</code> and comapre it.</p>