title: Composite foreign key is it possible?
body: <p>I have a tables:</p>
  
  <pre><code>CREATE TABLE test_part1 ( 
  
    Prefix ENUM('A','B') NOT NULL, 
    Unique_number int(11) NOT NULL, 
    Data_set1 decimal(5,2), 
    PRIMARY KEY (Prefix, Unique_number)
    ) ;
  
  CREATE TABLE test_part2 ( 
    composite_foregin_key tinytxt(12) NOT NULL, 
    Data1 varchar (11), 
    Data2 varchar (11) 
    ) ;
  </code></pre>
  
  <p>How can I reference composite key from “test_part1” in table “test_part2” as the foreign key?</p>
  
  <p>Do I need to create 2 columns called fkPrefix and fkUnique_number and use the same data types or can I create one column called composite_foregin_key? </p>
  
  <p>If option with composite_foregin_key is possible, do I need to change data type of composite key to Prefix txt (1) and Unique_ number txt (11) as the composite_foregin_key would be txt (12)? </p>
  
  <p>It is very important to me to join Prefix and Unique_number together as item under Unique_number is stored in either condition A or B and when referenced Prefix and Unique_ number are always together.</p>
  
  <p>I am trying to learn as much as possible about computer science but it’s not my field of expertise and before working on this project I was involved in basic db architecture really long time ago. Please be understanding if my question doesn’t make any sense. I will try to phrase it other way if needed. </p>