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Posted By

jmiller on 02/25/10


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sql count find duplicates


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Finding duplicates with SQL

 / Published in: SQL
 

URL: http://www.petefreitag.com/item/169.cfm

Here's a handy query for finding duplicates in a table.

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  1. # Suppose you want to find all email addresses in a table that exist more than once:
  2.  
  3. SELECT email, 
  4.  COUNT(email) AS count
  5. FROM users
  6. GROUP BY email
  7. HAVING ( COUNT(email) > 1 )
  8.  
  9.  
  10. # You could also use this technique to find rows that occur exactly once:
  11.  
  12. SELECT email
  13. FROM users
  14. GROUP BY email
  15. HAVING ( COUNT(email) = 1 )

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