紧急：返回表之间的重复记录 [英] Urgent: returning duplicate records between tables

问题描述

您好b $ b

我迫切需要一种方法在两张桌子中选择重复记录。



表1有A列和B列，有大约4000条记录

表2有A列和B列，有大约8000条记录



我想选择全部两个表中B都有重复值的记录。



以下查询应该有效，但产生20000条记录显然非常不正确。

Hi
I'm in urgent need of a way to select duplicate records in two tables.

Table1 has columns A and B and has around 4000 records
Table2 has columns A and B and has around 8000 records

I want to select all records which have a duplicate value for B in both tables.

The following query should work but produces 20000 records which is obviously wildly incorrect.

select Table1.A, Table1.B FROM Table1, Table2 WHERE Table1.B = Table2.B

我的尝试：



.................... .................................................. ..........................................

What I have tried:

................................................................................................................

推荐答案

使用 SQL INNER JOIN [ ^ ]

我认为B的相同值可以重复多次。检查这种情况的一种方法是使用 EXISTS 子句。



例如：

I take it that the same value for B can be repeated multiple times. One way to check this could be to use EXISTS clause.

For example:

SELECT *
FROM Table1 t1
WHERE EXISTS (SELECT 1 
              FROM Table2 t2
              WHERE t2.B = t1.B)

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