Question

我正在使用sqlite3查询学生数据库，其中只有 students 表。这里重要的列是省政府和等级。

我想查看每个省的90％以上的学生所占的百分比，所以我写了以下查询：

SELECT governorate, CASE
                WHEN grade > 360 AND grade <= 410 THEN '90%'
                WHEN grade > 320 THEN '80%'
                WHEN grade > 280 THEN '70%'
                WHEN grade > 240 THEN '60%'
                WHEN grade > 200 THEN '50%'
                WHEN grade > 160 THEN '40%'
                WHEN grade > 120 THEN '30%'
                WHEN grade > 80 THEN '20%'
                WHEN grade > 40 THEN '10%'
                WHEN grade > 0 THEN '0%'
                WHEN grade == 0 THEN '0'
             END AS bucket, COUNT(*) AS number FROM students GROUP BY 1, 2;

现在，这仅告诉您每个存储桶中的学生的数量，而不是总省学生的百分比。

它为每个省创建十行，我想要的是创建一个标记为 90-100 的新列，并对该列进行ORDER BY。

Answer 1

在SQLite中，您可以使用子查询：

SELECT governorate,
       (CASE WHEN grade > 360 AND grade <= 410 THEN '90%'
                WHEN grade > 320 THEN '80%'
                WHEN grade > 280 THEN '70%'
                WHEN grade > 240 THEN '60%'
                WHEN grade > 200 THEN '50%'
                WHEN grade > 160 THEN '40%'
                WHEN grade > 120 THEN '30%'
                WHEN grade > 80 THEN '20%'
                WHEN grade > 40 THEN '10%'
                WHEN grade > 0 THEN '0%'
                WHEN grade = 0 THEN '0'
             END) AS bucket,
        COUNT(*) AS number,
        COUNT(*) * 100.0 / c.cnt as percentage
FROM students s CROSS JOIN
     (SELECT COUNT(*) as cnt FROM students) c
GROUP BY 1, 2;

SQL GROUP BY作为新列

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