在 SQL 查询中添加一个只应过滤结果的列

Question

我有以下 table:

TABLE
+--------------------------+
| STUDENT  CLASS     SCORE |
+--------------------------+
| Student1 Science   Pass  |
| Student1 Math      Fail  |
| Student1 Geography Fail  |
| Student2 Science   Pass  |
| Student2 Math      Pass  |
| Student2 Geography Fail  |
+--------------------------+

我希望看到如下结果

+------------------------------------+
| STUDENT  Science   Math  Geography |
+------------------------------------+
| Student1 Pass     Fail   Fail      |
| Student2 Pass     Pass   Fail      |
+------------------------------------+

知道我该怎么做吗？

Answer 1

对于类的固定列表，您可以只使用条件聚合：

select student,
    max(case when class = 'Science'   then score end) as science,
    max(case when class = 'Math'      then score end) as math,
    max(case when class = 'Geography' then score end) as geography
from mytable
group by student

在 SQL 查询中添加一个只应过滤结果的列

Add a column in an SQL query that should only filtered results

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