sql - 错误 : aggregate function calls cannot be nested - POSTGRESQL

Question

我正在尝试创建一个包含 30 天内记录历史记录的选择，其中值列获得计数，我只希望它会添加每天返回的值。

查询

SELECT
    date_update AS Time,
    SUM(COUNT(values)) as "Value"
FROM
    tb_get_metrics
WHERE
    data_update >= CURRENT_DATE - 30
GROUP BY Time
ORDER BY Time

示例输出:

       Time                      Value
2019-10-14 09:46:54.789772        30
2019-10-15 09:46:54.789772        50
2019-10-16 09:46:54.789772        70

SELECT * FROM tb_get_metrics

  date_update(TimeStamp)        value(String)
2019-10-14 09:46:54.789772        apple
2019-10-14 09:46:55.789772        apple
2019-10-14 09:46:56.789772        apple
2019-10-14 09:46:57.789772        apple
2019-10-14 09:46:58.789772        apple
2019-10-14 09:46:59.789772        apple
2019-10-14 09:47:00.789772        apple
2019-10-14 09:46:01.789772        apple
2019-10-14 09:46:02.789772        apple
2019-10-14 09:46:03.789772        apple
2019-10-14 09:46:04.789772        apple
2019-10-14 09:46:05.789772        apple
2019-10-15 09:46:03.789772        potato
2019-10-15 09:46:04.789772        potato
2019-10-15 09:46:05.789772        potato
...

Answer 1

您需要将时间四舍五入到日期:

SELECT
    date_update::date AS "Date",
    COUNT(values) as "Value"
FROM
    tb_get_metrics
WHERE
    data_update >= CURRENT_DATE - 30
GROUP BY Time
ORDER BY Time