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Editorial Team
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Asked: 2026-05-23T01:05:19+00:00

I have a table like the one below. It is a record of daily

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I have a table like the one below. It is a record of daily featured products and the customers that purchased them (similar to a daily deal site). A given client can only purchase a product one time per feature, but they may purchase the same product if it is featured multiple times. 

FeatureID | ClientID | FeatureDate | ProductID  
 1           1002      2011-05-01      500  
 1           2333      2011-05-01      500  
 1           4458      2011-05-01      500  
 2           8888      2011-05-10      700  
 2           2333      2011-05-10      700  
 2           1111      2011-05-10      700    
 3           1002      2011-05-20      500  
 3           4444      2011-05-20      500  
 4           4444      2011-05-30      500  
 4           2333      2011-05-30      500  
 4           1002      2011-05-30      500

I want to count by FeatureID the number of clients that purchased FeatureID X AND who purchased the same productID during a previous feature.

For the table above the expected result would be:

FeatureID | CountofReturningClients  
 1          0  
 2          0  
 3          1  
 4          3

Ideally I would like to do this with SQL, but am also open to doing some manipulation in Excel/PowerPivot. Thanks!!

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1 Answer

  1. Editorial Team

    If you join your table to itself, you can find the data you’re looking for. Be careful, because this query can take a long time if the table has a lot of data and is not indexed well.

    SELECT t_current.FEATUREID, COUNT(DISTINCT t_prior.CLIENTID)
FROM table_name t_current
LEFT JOIN table_name t_prior
ON t_current.FEATUREDATE > t_prior.FEATUREDATE
AND t_current.CLIENTID = t_prior.CLIENTID
AND t_current.PRODUCTID = t_prior.PRODUCTID
GROUP BY t_current.FEATUREID
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