How to Find Unique Maximum Values for Grouped Data in a Table?

Find the maximum value of grouped data

Given a table with multiple columns, a common task is to identify the maximum value within a specific group. In the example provided, we have data related to the pumps (Pump1 and Pump2) with different values ​​and an additional column (AnotherColumn) . The goal is to retrieve the maximum value for each pump.

One approach might involve using a subquery to select the maximum value grouped by the name column:

<code class="language-sql">select name, max(value) as value
from out_pumptable
group by name</code>

However, as mentioned in the question, this approach may be possible if there are multiple maxima for a certain group (in this case, Pump 1 has two entries with the same max) Duplicate entries will be returned.

To solve this problem, you can use the DISTINCT keyword to ensure that only distinct maximum values ​​are returned:

<code class="language-sql">select name, max(value) as value
from out_pumptable
group by name
having max(value) not in (select value from out_pumptable group by value having count(*) > 1)</code>

This modification checks if the maximum value is unique across the table (using a subquery). If the value is not unique, it is excluded from the results. This method more accurately represents the maximum value for each pump.

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