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7.8

Syntax to get most recent N rows for each entity in a table

Asked by TruthHunter in Databases Miscellaneous, Data Mining, MySQL Server

Tags: SQL, Any, N/A

Hi,

This is a follow-up to the question at: http://www.experts-exchange.com/Database/Miscellaneous/Q_23739459.html

Given the same table:

column A identifies the entity generating the data
column B contains the data
column C is the timestamp of when the data was generated

I now need to be able to get the most recent N rows (say, 5) for each entity.

The solution from the other question link above gets the most recent one row for each entity:

SELECT t1.A, t1.B
FROM Table AS t1 INNER JOIN
(SELECT t2.A, MAX(t2.C) AS maxTime
FROM Table AS t2
GROUP BY t2.A) AS t3 ON t1.A = t3.A AND t1.C = t3.maxTime
ORDER BY t1.A

Is there any way to expand this to get the most recent N rows for each entity as opposed to only the single most recent row? Max points on tap again - thanks!

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20091111-EE-VQP-92 / EE_QW_2_20070628

Syntax to get most recent N rows for each entity in a table

Asked by TruthHunter in Databases Miscellaneous, Data Mining, MySQL Server

Tags: SQL, Any, N/A

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