Your question is a bit cryptic. The title says SQL query and update attributes. But your question says CSV.

I guess you have a dataset with more than 1 measurement per bore hole? Does the dataset contain multiple bore holes? Or just 1?

And your desired output is that all measurements have 1 extra attribute 'end depth' with the max('depth')

There is more than 1 way to Rome.

1. You could use an Sorter-AttributeCreator Combination. The AttributeCreator has a function to look at the previous feature. If that feature is the same bore hole, use that features 'end depth' as 'end depth' of your current feature.
2. Use the InlineQuerier as you where trying n SELECT * FROM "Sampled" LEFT JOIN (SELECT "hole",max("depth") as 'end depth' FROM "Sampled" GROUP BY "hole") AS "Table" WHERE "Sampled"."hole" = "Table"."hole" ]
3. You could use a StatisticsCalculator. The Complete Output has the values you need.
4. The Sorter-Sampler-FeatureMerger combination is also possible. Sort so that the bore hole measurement with the largest value comes first. Sample 1 feature grouped by bore hole and merge this feature back to your original Dataset.

There are probably more solutions.

Thanks mate.

In the end I went back to the InlineQuerier to perform the query to strip out the records i wanted to update.

Then i used FeatureMerger and Attribute Manager to update the records.

Probably not the most elegant solution but it works.