如果不存在或不存在

Question

所有论文表ERTBatches,ERTBatchChecks,ERTClaims有一个标识符.
假设标识符是1010.
此标识符必须存在于所有三个表中.

我试图找出是否所有三个表中都没有任何标识符.

这些是标识符的名称:

ERTBatches."BatchIdentifier"
ERTClaims."ERTBatchNumber"
ERTBatchChecks."BatchIdentifier"

Answer 1

一种方法是union all聚合:

select id
from ((select b.BatchIdentifier as id, 1 as which from ERTBatches b) union all
      (select bc.BatchIdentifier as id, 2 as which from ERTBatchChecks bc) union all
      (select c.ERTBatchNumber as id, 3 as which from ERTClaims c)
     ) t
group by id
having count(distinct which) < 3;