mysql 获取字段值总和

Posted 2023-04-17

$sql ="select sum(dingdan_price) from dingdan";
$re = mysql_query($sql);
var_dump($re);
为什么打印的结果是resource(5) of type (mysql result)
我有个dingdan表 然后dingdan_price里边存的是每条订单记录卖的金额
想把所有记录的金额相加

$sql ="select sum(dingdan_price) from dingdan";
$re = mysql_query($sql);
list($sum)=mysql_fetch_row($re);
mysql_free_result($re);
echo "总和=$sum"; 参考技术A select sum(line) from dx_member

呃,既然解决了,就多加一句,有什么SQL语句的问题可以参考这个网站,
http://www.w3school.com.cn/sql/index.asp

如何计算mysql中多个条件值的总和

【中文标题】如何计算mysql中多个条件值的总和

【英文标题】：how to calculate of sum of multiple conditional values in mysql

【发布时间】：2021-03-18 07:05:24

【问题描述】：

我正在尝试获取条件值的总和并按分钟分组。

我成功完成了以下查询，但结果需要一些时间，想知道有什么有效的方法吗？

SELECT x.query, x.value, x.time FROM (
    SELECT id, query, SUM(VALUE) AS value, time FROM `modbuslogs` WHERE query IN ("sensor1","sensor2") AND time LIKE '2020-12-04%' GROUP BY HOUR(time), MINUTE(TIME) 
    UNION
    SELECT id, query, SUM(VALUE) AS value, time FROM `modbuslogs` WHERE query IN ("sensor3","sensor4") AND time LIKE '2020-12-04%' GROUP BY HOUR(time), MINUTE(TIME) 
) x
GROUP BY x.query, HOUR(time), MINUTE(TIME) 
ORDER BY x.id

表结构：

+--------+-------+-----------------+
|  query | value |       time      |
+--------+-------+-----------------+
|sensor1 |   2   |2012-02-10 00:00 |
|sensor2 |   2   |2012-02-10 00:00 |
|sensor3 |   3   |2012-02-10 00:00 |
|sensor4 |   3   |2012-02-10 00:00 |
|sensor1 |   2   |2012-02-10 00:01 |
|sensor2 |   3   |2012-02-10 00:01 |
|sensor3 |   3   |2012-02-10 00:01 |
|sensor4 |   2   |2012-02-10 00:01 |
+--------+-------+-----------------+

获得和预期的输出：

+--------+-------+-----------------+
|  query | value |       time      |
+--------+-------+-----------------+
|sensor1 |   4   |2012-02-10 00:00 |
|sensor3 |   6   |2012-02-10 00:00 |
|sensor1 |   5   |2012-02-10 00:01 |
|sensor3 |   5   |2012-02-10 00:01 |
+--------+-------+-----------------+

【参考方案1】：

首先，union 子查询毫无意义。这相当于您的查询：

select id, query, sum(value) as value, min(time) as time
from modbuslogs
where 
    query in ('sensor1', 'sensor2', 'sensor3', 'sensor4')
    and time >= '2020-12-04'
    and time <  '2020-12-05'
group by query, hour(time), minute(time)

这为每 query 和每分钟提供一行，总和为 value。并不是说我们需要围绕time 的聚合函数，所以select 子句与group by 子句是一致的。此外，where 子句使用日期过滤而不是字符串匹配。

另一方面，如果您希望将两组传感器放在两个不同的列中，则使用条件聚合：

select id, min(time) as time,
    sum(case when query in ('sensor1', 'sensor2') then value else 0 end) as value_1_2, 
    sum(case when query in ('sensor3', 'sensor4') then value else 0 end) as value_3_4
from modbuslogs
where 
    query in ('sensor1', 'sensor2', 'sensor3', 'sensor4')
    and time >= '2020-12-04'
    and time <  '2020-12-05'
group by hour(time), minute(time)

【讨论】：

我使用了您的第二个查询。好极了。非常感谢