SQL查询（使用连接）/递归

Question

我有3个表：AuditCheckCriteria为T1，学习者为T2＆amp; LearnerAuditRegistrations为T3，具有以下结构：

  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

我想要以下输出：

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＆amp; T3每个包含超过20000行）

感谢任何帮助！

Answer 1

看起来你想要T1和T2的所有值组合，以及来自T3的查找。如果是这样，以下是这样的：

with t1vals as (select distinct checkID from t1),
     t2vals as (select distinct LearnerId from t2)
select t2vals.LearnerId, t1vals.CheckId, t3.CheckId
from t1vals cross join
     t2vals left outer join
     t3
     on t3.LearnerId = t2vals.LearnerId and
        t3.CheckId = t1vals.CheckId

Answer 2

使用（T2交叉连接T1）左连接T3 ..