Question

我试图仅消除两个字段与另一个表中给定值匹配的记录。

SELECT CODE, NUM 
FROM TABLE_A
WHERE  (CODE not in (SELECT CODE FROM TABLE_B) AND NUM not in (SELECT NUM FROM TABLE_B))

然而，这似乎消除了具有这些值之一的所有记录。我只需要消除两个都匹配TABLE2给定记录的记录。 OR在这里看似违反直觉吗？

Answer 1

SELECT CODE, NUM 
FROM TABLE_A TA
WHERE  
not exists (select 1 from TABLE_B TB where TB.CODE=TA.CODE)
and 
not exists (select 1 from TABLE_B TB where TB.NUM=TA.NUM)

Answer 2

SELECT CODE, NUM 
FROM TABLE_A a
WHERE NOT EXISTS (SELECT 1 FROM TABLE_B b where b.CODE = a.CODE and b.NUM = a.NUM);

EXISTS关键字测试子查询中是否存在任何行。如果没有找到行，则答案为FALSE。否则，子查询返回TRUE。 NOT EXISTS反转结果。

Answer 3

如果您担心NOT EXISTS的性能，您还可以尝试使用LEFT OUTER JOIN和WHERE子句检查相同的条件：

SELECT 
    a.CODE, 
    a.NUM 
FROM 
    TABLE_A a
     LEFT OUTER JOIN -- return all from table A, and matches from table B
    TABLE_B b ON 
        a.CODE = b.CODE AND 
        a.NUM = b.NUM 
WHERE b.CODE IS NULL -- filter out the ones that matched; think of this as a reverse INNER

检查记录中的两个字段

3 个答案: