mysql按照小时
时间: 2023-07-01 14:28:35 浏览: 41
如果您想在MySQL中按小时进行查询,可以使用DATE_FORMAT函数将日期时间戳转换为小时格式,然后使用GROUP BY子句将结果按小时分组。
以下是一个示例查询,该查询将按小时统计订单数量:
```
SELECT DATE_FORMAT(order_date, '%Y-%m-%d %H:00:00') AS hour, COUNT(*) AS order_count
FROM orders
GROUP BY hour;
```
该查询将订单日期(order_date)转换为 '%Y-%m-%d %H:00:00' 格式的小时,并将结果按小时分组。您可以根据您的具体需求修改查询中的表名、列名和格式。
相关问题
MYSQL按照小时;按天;按月分组,无数据补0
可以使用 MySQL 的日期函数和 GROUP BY 子句来按照小时、天和月分组。
按小时分组:
```
SELECT DATE_FORMAT(date_column, '%Y-%m-%d %H:00:00') as hour, COUNT(*) as count
FROM table_name
GROUP BY hour;
```
按天分组:
```
SELECT DATE(date_column) as day, COUNT(*) as count
FROM table_name
GROUP BY day;
```
按月分组:
```
SELECT DATE_FORMAT(date_column, '%Y-%m') as month, COUNT(*) as count
FROM table_name
GROUP BY month;
```
如果需要在无数据的情况下补0,可以使用 MySQL 的 IFNULL 函数和子查询来实现:
按小时分组:
```
SELECT hours.hour, IFNULL(data.count, 0) as count
FROM (
SELECT DATE_FORMAT(date_column, '%Y-%m-%d %H:00:00') as hour
FROM table_name
GROUP BY hour
) as hours
LEFT JOIN (
SELECT DATE_FORMAT(date_column, '%Y-%m-%d %H:00:00') as hour, COUNT(*) as count
FROM table_name
GROUP BY hour
) as data ON hours.hour = data.hour;
```
按天分组:
```
SELECT days.day, IFNULL(data.count, 0) as count
FROM (
SELECT DATE(date_column) as day
FROM table_name
GROUP BY day
) as days
LEFT JOIN (
SELECT DATE(date_column) as day, COUNT(*) as count
FROM table_name
GROUP BY day
) as data ON days.day = data.day;
```
按月分组:
```
SELECT months.month, IFNULL(data.count, 0) as count
FROM (
SELECT DATE_FORMAT(date_column, '%Y-%m') as month
FROM table_name
GROUP BY month
) as months
LEFT JOIN (
SELECT DATE_FORMAT(date_column, '%Y-%m') as month, COUNT(*) as count
FROM table_name
GROUP BY month
) as data ON months.month = data.month;
```
mysql 8小时断开
MySQL默认情况下会在连接空闲时间超过8小时后自动断开该连接。这是由于MySQL的两个参数interactive_timeout和wait_timeout默认值都是28800秒(8小时)导致的。如果需要更改这些参数的值,可以通过修改MySQL配置文件或者在MySQL客户端中执行相应的SQL语句来实现。下面是两种方法:
1. 修改MySQL配置文件
可以通过修改MySQL配置文件my.cnf或者my.ini来更改interactive_timeout和wait_timeout的值。在文件中添加以下两行代码即可:
```
interactive_timeout=3600
wait_timeout=3600
```
这里将这两个参数的值都设置为3600秒(1小时)。修改完毕后,需要重启MySQL服务才能生效。
2. 在MySQL客户端中执行SQL语句
可以在MySQL客户端中执行以下两条SQL语句来更改interactive_timeout和wait_timeout的值:
```
SET interactive_timeout=3600;
SET wait_timeout=3600;
```
这里同样将这两个参数的值都设置为3600秒(1小时)。执行完毕后,可以通过以下语句来验证是否修改成功:
```
SHOW VARIABLES LIKE '%timeout%';
```
该语句会显示MySQL中所有与timeout相关的参数及其当前值。