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by radiospiel
1986 days ago
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> If SQL had a way of picking one row from a group, rather than aggregating over it, that would be immensely useful. Well, there is a way which is window functions :) as shown by you. The idea to expect exactly one first name of the person with the biggest salary is kinda wrong, since there can be more than one person, and this can obviously not described as a single column per group. Note that aggregating is not limited to min, max, sum, etc. Postgres, for example, has array_agg which aggregates individual columns from each record of a group into an array, if that becomes necessary. |
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That's true. For this idea to work, there would need to be some framework for picking exactly one row from a group. The simplest thing would be to raise an error if there were multiple candidates, but perhaps there are better ways. I think the operation of picking exactly zero or one things from a group is so common that it's worth making provision for it.