MYSQL sql在count大于x的表中查找id

Question

I have a table which has the raw data. In order to check for unwanted extra data I am trying to determine what id's (tickerid is the column, earningsdata is the table) have more than 50 rows of data. It would have to loop through all the current ticker id's (from a different table, earningstickers) and select only those id's that have more than 50 rows of data. I can do a select * by id but I'm not sure how to iterate through all the id's

Answer 1

You can use GROUP BY to group by each tickerid , which will give you access to aggregate information related to each tickerid such as COUNT / SUM / AVG /etc...

For your purposes, we must use COUNT .

Then the HAVING clause filters out the tickerid s that have 50 rows or less:

SELECT tickerid
FROM earningsdata
GROUP BY tickerid
HAVING COUNT(*) > 50

This will just give you a list of the tickerid s that have more than 50 rows, however if you want to display all rows and information of the tickerid s that are in this list, you can join the table against this list by incorporating the above query into:

SELECT a.*
FROM earningsdata a
INNER JOIN
(
    SELECT tickerid
    FROM earningsdata
    GROUP BY tickerid
    HAVING COUNT(*) > 50
) b ON a.tickerid = b.tickerid

Answer 2

SELECT tickerid 
FROM earningstickers 
WHERE tickerid 
IN 
    (SELECT tickerid
     FROM earningsdata
     GROUP BY tickerid
     HAVING COUNT(*) > 50
     )