验证两个不同表的两列完全匹配

Question

在深层视图中编写视图和嵌套视图时,我有时会遗漏某些内容并最终丢失行/数据.如何检查两个不同表中的列是否具有完全匹配的数据？

例:

select count(distinct table1.col1)
  from table1
 where table1.col1 not in (select distinct table2.col1 
                             from table2);

这将返回table1.col1中不在table2中的值的数量.但是,我不知道这是一个很好的解决方案,因为它不计算table1.col1中不存在的table2.col1值.

Answer 1

您可以使用两个EXCEPT查询(或联合它们)来检查:

SELECT DISTINCT col1
FROM table1
EXCEPT
SELECT DISTINCT col1
FROM table2

这将显示table1中存在的值,但不显示table2中的值.然后再次运行,表格名称翻转为相反.

Answer 2

使用：

SELECT MAX(x.t1_missing_count) AS t1_missing_count, 
       MAX(x.t2_missing_count) AS t2_missing_count
  FROM (
SELECT COUNT(DISTINCT t1.col1) AS t1_missing_count,
       NULL AS t2_missing_count
  FROM TABLE_1 t1
 WHERE t1.col1 NOT IN (SELECT DISTINCT t2.col1 
                         FROM TABLE_2 t2)
UNION ALL
SELECT NULL,
       COUNT(DISTINCT t2.col1),           
  FROM TABLE_2 t2
 WHERE t2.col1 NOT IN (SELECT DISTINCT t1.col1 
                         FROM TABLE_1 t1)) x