Sql 在单个查询中使用多个计数

我在下面有一个查询，我想返回一天的关键和警告警报总数，但我的问题是，当我在一定的天数范围内执行此操作时，它会添加指定日期的关键警报

SELECT alertDate as "Alert Date",
    (SELECT COUNT(alertType) FROM alerts WHERE alertDate BETWEEN '2016/02/15' AND '2016/02/16' AND UPPER(alertType)='CRITICAL') as Critical,
    (SELECT COUNT(alertType) FROM alerts WHERE alertDate BETWEEN '2016/02/15' AND '2016/02/16' AND UPPER(alertType)='WARNING') as Warning
FROM alerts
where alertDate BETWEEN '2016/02/15' AND '2016/02/16'
GROUP BY alertDate;

尝试了上面的代码，但显然我无法在子查询中添加“group by”子句，我认为这就是问题所在，请提供有关如何进行此操作的帮助…

您可以使用sum（case）来实现此目的：

SELECT alertDate as "Alert Date",
    sum(case when UPPER(alertType)='CRITICAL' then 1 end) as Critical,
    sum(case when UPPER(alertType)='WARNING' then 1 end) as Warning
FROM alerts
where alertDate BETWEEN '2016/02/15' AND '2016/02/16'
GROUP BY alertDate;

您可以使用sum（case）进行以下操作：

SELECT alertDate as "Alert Date",
    sum(case when UPPER(alertType)='CRITICAL' then 1 end) as Critical,
    sum(case when UPPER(alertType)='WARNING' then 1 end) as Warning
FROM alerts
where alertDate BETWEEN '2016/02/15' AND '2016/02/16'
GROUP BY alertDate;

---

您需要条件聚合--

案例

位于聚合函数内部。我将这样写：

SELECT alertDate as AlertDate,
       SUM(CASE WHEN UPPER(alertType) = 'CRITICAL' THEN 1 ELSE 0 END) as Critical,
       SUM(CASE WHEN UPPER(alertType) = 'WARNING' THEN 1 ELSE 0 END) as WARNING
FROM alerts a
WHERE alertDate BETWEEN '2016-02-15' AND '2016-02-16'
GROUP BY alertDate;

如果您使用的是MySQL，您可以将其短接到：

SELECT alertDate as AlertDate,
       SUM(UPPER(alertType) = 'CRITICAL') as Critical,
       SUM(UPPER(alertType) = 'WARNING') as Warning
FROM alerts a
WHERE alertDate BETWEEN '2016-02-15' AND '2016-02-16'
GROUP BY alertDate;

请注意其他几个变化：

• 不需要子选择
• 我删除了

  AlertDate

  中的空格。我只是不喜欢需要转义的列别名
• 我将日期文本中的

  /

  替换为

  -

  ——连字符与ISO 8601兼容

---

您需要条件聚合--

大小写在聚合函数中。我将这样写：

SELECT alertDate as AlertDate,
       SUM(CASE WHEN UPPER(alertType) = 'CRITICAL' THEN 1 ELSE 0 END) as Critical,
       SUM(CASE WHEN UPPER(alertType) = 'WARNING' THEN 1 ELSE 0 END) as WARNING
FROM alerts a
WHERE alertDate BETWEEN '2016-02-15' AND '2016-02-16'
GROUP BY alertDate;

如果您使用的是MySQL，您可以将其短接到：

SELECT alertDate as AlertDate,
       SUM(UPPER(alertType) = 'CRITICAL') as Critical,
       SUM(UPPER(alertType) = 'WARNING') as Warning
FROM alerts a
WHERE alertDate BETWEEN '2016-02-15' AND '2016-02-16'
GROUP BY alertDate;

请注意其他几个变化：


不需要子选择
我删除了
AlertDate
中的空格。我只是不喜欢需要转义的列别名
我将日期文本中的
/
替换为
-
——连字符与ISO 8601兼容
您可能应该使用如下条件计数

SUM( case when alertDate BETWEEN '2016/02/15' AND '2016/02/16' 
     AND UPPER(alertType)='CRITICAL' then 1 else 0 end) as Critical,

您可能应该使用条件计数，如

SUM( case when alertDate BETWEEN '2016/02/15' AND '2016/02/16' 
     AND UPPER(alertType)='CRITICAL' then 1 else 0 end) as Critical,

您能否提供一些您的查询没有解决的预期结果？您可以选择MySQL或SQL Server吗？它们都非常不同…我删除了不兼容的数据库标记。请用您真正使用的数据库进行标记。很抱歉，我使用的是SQLServer。您能否向我们提供一些您的查询未解决的预期结果？您能否选择MySQL或SQL Server？它们都非常不同…我删除了不兼容的数据库标记。请使用您真正使用的数据库进行标记。对不起，我使用的是sqlserver