如何在两个表中提取非重复值(How to extract non

如何在两个表中提取非重复值(How to extract non-duplicate values in two tables)

我有两个表，每个表包含带数字的列。 我需要比较两个表中的列并提取第一个表中存在的数字，而不是第二个表中存在的数字。 我不需要独特的价值。

我写了这个查询：

SELECT Table1.Numbers, Table1.Name FROM Table1, Table2 WHERE Table1.Numbers != Table2.numbers

由于我正在处理数百万条记录，有人可以推荐更有效的查询，这会给我提供相同的结果吗？

I have two tables where each one contains columns with numbers. I need to compare columns in both tables and extract the number that does exist in first table, and does not exist in second one. I don't need unique value.

I wrote this query:

SELECT Table1.Numbers, Table1.Name FROM Table1, Table2 WHERE Table1.Numbers != Table2.numbers

Since I am working on several million records can someone recommend more efficient query which would provide me with identical results?

最满意答案

我会使用NOT EXISTS ：

SELECT Table1.Numbers, Table1.Name FROM Table1 WHERE NOT EXISTS( SELECT 1 FROM Table2 WHERE Table1.Numbers=Table2.Numbers )

其他方法：

我应该使用NOT IN，OUTER APPLY，LEFT OUTER JOIN，EXCEPT还是NOT EXISTS？

I would use NOT EXISTS:

SELECT Table1.Numbers, Table1.Name FROM Table1 WHERE NOT EXISTS( SELECT 1 FROM Table2 WHERE Table1.Numbers=Table2.Numbers )

Other approaches:

Should I use NOT IN, OUTER APPLY, LEFT OUTER JOIN, EXCEPT, or NOT EXISTS?