查找同一表中缺失的行

问题描述

我有一个 sql 表，如下所示。我想为所有具有 B1 的 ColA 找到缺失的 B2。

Id	ColA	ColB
1	A1	B1
2	A1	B2
3	A2	B1
4	A3	B1

预期结果：A2,A3

解决方法

不确定这是您所期望的。

 select ColA from table where ColB = 'B1' 
    and ColA not in (select ColA from table where ColB = 'B2')

,

如果您的数据库支持 WITH，那么您可以：

  WITH 
     with_b1 AS (SELECT DISTINCT ColA FROM t WHERE ColB = 'B1'),with_b2 AS (SELECT DISTINCT ColA FROM t WHERE ColB = 'B2')
SELECT ColA 
  FROM with_b1
 WHERE ColA NOT IN (SELECT ColA FROM with_b2)

否则试试

SELECT ColA 
  FROM (SELECT DISTINCT ColA FROM t WHERE ColB = 'B1')
 WHERE ColA NOT IN (SELECT ColA FROM t WHERE ColB = 'B2')

,

您需要 GROUP BY 和 HAVING 如下：

select colA
 from your_Table t
group by colA
Having count(distinct colB) <> (select count(distinct tt.colB) from your_Table tt)