Urgent: returning duplicate records between tables

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1.00/5 (2 votes)

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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.

SQL

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

What I have tried:

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

Posted 25-Sep-17 8:17am

User 13204940

Updated 25-Sep-17 10:06am

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OriginalGriff · Answer 1 · 2017-09-25T08:32:00

Solution 1

Use an SQL INNER JOIN[^]

Posted 25-Sep-17 8:32am

OriginalGriff

Wendelius · Answer 2 · 2017-09-25T10:06:00

Solution 2

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:

SQL

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

Posted 25-Sep-17 10:06am

Wendelius