SQL query (using joins) / recursion
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I have 3 tables: AuditCheckCriteria as T1, Learners as T2 & LearnerAuditRegistrations as T3 with the following structure:

   

      T1: CheckID     CheckName                      
              1       'Stage One'
              2       'Stage Two'
              3       'Stage Three'
        
      T2   LearnerID   LearnerName
              10         'John'
              11         'Peter'
              12         'Paul'
    
      T3: LearnerAuditID  LearnerID  CheckID
              1             10         1
              2             10         2
              3             11         1
              4             11         2
              5             11         3

I want the following output:

    T2.LearnerID, T1.CheckID, T3.CheckID
          10           1           1
          10           2           2
          10           3          NULL
          11           1           1
          11           2           2
          11           3           3
          12           1          NULL
          12           2          NULL
          12           3          NULL

(T2 & T3 contain over 20000 rows each)

Any help is appreciated!