title: SSIS Union All does not return all the records
body: <p>Very beginner question please. I have a simple script that performs a lookup for records in a different table - in this case the doctor who was assigned for treatments of a patient. Due to the lack of data quality control, a number of records do not have the correct doctor id assigned therefore the lookup returns non-matching output. I then have to create a dummy doctor for those records. After that I would like to merge the 2 record-sets into 1. </p>
  
  <p>In my test database, I have a total of 20 599 records. The lookup transformation returns with 9 124 records that provide no-matching output and 11 475 records that do. What I dont understand is when I do a Union All, the result only comes up with a total 17 885 records. (please see the screenshot below, problem occurs @ Find Servicing Doctor then Union All) </p>
  
  <p>Never had this problem before. I use the same technique several times in other section of this script and they all return the correct number of records. Any help would be greatly appreciated</p>
  
  <p><img src="https://i.stack.imgur.com/cvhjh.png" alt="Screenshot showing the number of records"></p>