Question

I have a database with 1000 records containing a file name and a file size on each row.
If the SUM of all file sizes exceeds a specific limit, then:
– I need to create a sql query to delete all the remaining rows, from oldest to newest

Any suggestions?
Thanks

Answer 1

Supposing a table created thus:

CREATE TABLE Files (Id INTEGER PRIMARY KEY, FileName TEXT, CreationDate DATE, Size INTEGER);

To get the running sum, use the following query:

SELECT f1.id AS FileId, sum(f2.size) AS RunningSumSize
FROM file f1 INNER JOIN file f2
ON f1.createdDate<=f2.createdDate
GROUP BY FileId
ORDER BY RunningSumSize DESC;

To delete the file ID’s above the threshold:

DELETE FROM File WHERE Id IN
 (SELECT FileId FROM 
  (SELECT f1.id AS FileId, sum(f2.size) AS RunningSumSize
  FROM file f1 INNER JOIN file f2
  ON f1.createdDate<=f2.createdDate
  GROUP by FileId
  ORDER by RunningSumSize DESC)
  WHERE RunningSumSize > :ThresholdSize:);

Note: The order by is optional.