teradata row_number() over(partition by X , Y order by Z desc) = 1
<p>I often use this in Teradata SQL assistant:</p>

<pre><code>row_number() over(partition by X||Y order by Z desc) = 1
</code></pre>

<p>My colleague uses the same BUT with the difference that he doesn't enter "||" between two attributes, he just enters a ",". I tested some small data with both and could not find any difference in the output. </p>

<p>My assumption was that using "||" is kind of a concatenation of the two attributes (X and Y). Is this true or not?</p>

<p>Does somebody now what the difference is between "||" and "," in this command?</p>

<p>Many thanks in advance..</p>