一列接另一列的SQL组值 [英] SQL group values for one column by another column

问题描述

SQL中是否存在某种仅将值转换为列表的聚合"函数?一个示例可能是以下形式的表:

Is there some kind of "aggregate" function in SQL that just turns values into a list? An example might be a table of the form:

| game_id | player | score |
|---------|--------|-------|
|   1     | fred   | 2     |
|   1     | tom    | 1     |
|   2     | fred   | 3     |
|   2     | tom    | 4     |

我想要返回的是一个看起来像这样的表:

What I would like returned is a table that looks like this:

| player | scores |
|--------|--------|
|   fred | 2, 3   | 
|   tom  | 1, 4   |

该命令可能类似于: SELECT player, listify(score) FROM games GROUP BY player;

The command might look something like: SELECT player, listify(score) FROM games GROUP BY player;

推荐答案

感谢Tim和Gordon.我正在寻找的Postgres函数是array_agg.在这种情况下，完整查询如下所示:

Thanks to Tim and Gordon. The Postgres function I'm looking for is array_agg. The full query in this case looks like this:

SELECT player, array_to_string(array_agg(score), ',') AS scores FROM games GROUP BY player;

array_agg将所有乐谱放入一个数组中，您必须将它们转换为字符串才能在SELECT语句中返回它们.

array_agg puts all the scores into an array, and you have to convert them to a string to be able to return them in a SELECT statement.

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