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Editorial Team
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Asked: 2026-06-12T08:07:28+00:00

I have a MySQL table with a large amount of records (~20k), which is

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I have a MySQL table with a large amount of records (~20k), which is in 1NF. Unfortunately converting it to 2NF and above is not an option here.

The Table contains data such as 

ClientName1 | ClientLastName1 | ClientZip1 | ... | Product1
ClientName1 | ClientLastName1 | ClientZip1 | ... | Product2
ClientName1 | ClientLastName1 | ClientZip1 | ... | Product3
ClientName2 | ClientLastName2 | ClientZip2 | ... | ProductX
ClientName3 | ClientLastName3 | ClientZip3 | ... | Product1
ClientName3 | ClientLastName3 | ClientZip3 | ... | Product2
ClientName4 | ClientLastName4 | ClientZip4 | ... | Product2
ClientName4 | ClientLastName4 | ClientZip4 | ... | Product3

What i would like to do is to get all the products of a client who has at least Product1.
So in the example above that would be the following records:

ClientName1 | ClientLastName1 | ClientZip1 | ... | Product1
ClientName1 | ClientLastName1 | ClientZip1 | ... | Product2
ClientName1 | ClientLastName1 | ClientZip1 | ... | Product3
ClientName3 | ClientLastName3 | ClientZip3 | ... | Product1
ClientName3 | ClientLastName3 | ClientZip3 | ... | Product2

For now lets assume (ClientName,ClientLastname) are unique for each client.
I used the following query assuming the the Table Name is clients

SELECT 
  ClientID
FROM
 clients cl 
WHERE (ClientName,ClientLastname) 
  IN ( 
    SELECT ClientName, ClientLastname
    FROM clients 
    GROUP BY ClientName,ClientLastname,Product 
    HAVING Product IN (Product1ID)
)

First of all this query runs for ages, and seems not to terminate (or at least not in a reasonable time) and second of all i think it is not correct.

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1 Answer

  1. Editorial Team

    In an ideal world, my suggestion would be to try to normalize this table, as much as possible. As you can see, you have a mess of a table to try to work with.

    But have you tried something like this (See SQL Fiddle with Demo):

    select c.ClientName, 
  c.ClientLastName,
  c.ClientZip,
  c.Product
from clients c
inner join 
(
  select ClientName
  from clients
  where Product = 'Product1' 
) x
  on c.ClientName= x.ClientName
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