Why do these queries produce different results?

[James Armstrong]

I am new to MySQL and have been trying to create a query that will return records with the lowest LTP per MarketName/SelectionName.

I have two different approaches but they return a different number of records when - to my beginner knowledge - they should return the same. The second query returns around 10% more records than the first.

There's nothing obvious in the data.

Can someone see what the issue is?

Thanks

First query:

WITH cte AS (
SELECT *,
ROW_NUMBER() OVER (PARTITION BY MarketName, SelectionName ORDER BY LTP) AS rn,
COUNT(*) OVER (PARTITION BY MarketName, SelectionName) AS count
FROM r.`20224`
WHERE MarketState = 'Not In Play' AND SelectionID <> 0 AND CloseTime <> '' AND Result <> ''
)
SELECT * -- here you can select only the columns that you need
FROM cte
WHERE rn = 1 AND count > 900

Second query:

SELECT r.`20224`.*, null, null from r.`20224`,
(SELECT MarketName, SelectionName, MIN(`Date/Time`) AS `Date/Time` FROM r.`20224` WHERE MarketState = "Not In Play" AND SelectionID <> 0 AND CloseTime <> "" AND Result <> "" GROUP BY MarketName, SelectionName HAVING COUNT(*) > 900) min_LTP
WHERE r.`20224`.SelectionName=min_LTP.SelectionName
AND r.`20224`.`Date/Time`=min_LTP.`Date/Time`