Home Database Mysql Tutorial mysql惯用的日期函数汇总

mysql惯用的日期函数汇总

Jun 07, 2016 pm 04:23 PM
mysql function date Summary use

mysql常用的日期函数汇总 最近做统计时经常用到的几个mysql函数: 1. UNIX_TIMESTAMP()? 该函数返回1970到现在的秒数,括号内也可以带参数,即返回1970年到指定时间段的秒数,注意是秒数,常用java的兄弟们需要注意,因为java中的System.currentTimeMillis()

mysql常用的日期函数汇总

最近做统计时经常用到的几个mysql函数:

1. UNIX_TIMESTAMP()?

该函数返回1970到现在的秒数,括号内也可以带参数,即返回1970年到指定时间段的秒数,注意是秒数,常用java的兄弟们需要注意,因为java中的System.currentTimeMillis()返回的是毫秒数

?

2. date_format()

举一个例子 date_format(now(), '%Y-%m-%d %H:%i:%s') 将当前时间转换成某种时间格式的字符串,当然now()函数的默认格式已经是 '%Y-%m-%d %H:%i:%s'

?

3. FROM_UNIXTIME()

FROM_UNIXTIME(1390357150,'%Y-%m-%d'); 将返回1970年到指定时间段的秒数,转换成固定的时间格式,

这个适用于后台日期存放的是秒数,前台展示时需要的是具体的某种日期的应用

?

4. current_date()

这个函数的作用是返回当前的日期,但是这个函数在日期做减法时是会有Bug的,

以今天为例:

select current_date();

2014-01-24

我想知道今天以前的30天的日期

select current_date()-30;

20140094

显然不是我们想得到的值,经过测试发现当涉及到月份或年份的退位进位时就会出错

对于求今天之前的三十天,可以利用毫秒数做

select FROM_UNIXTIME(UNIX_TIMESTAMP(current_date())-24*60*60*30,'%Y-%m-%d');

哪位大神有更好的方法,欢迎指导

?

利用以上函数,就可以做简单的基于在线数量的统计,

相关表

? user_online_count_tbl

相关字段

? user_online_num(当前用户在线数)

? online_statistic_time(统计在线数时的时间)

?

?

5.基于最近10天的平均在线用户数统计

select 
  sum(user_online_num)/count(online_statistic_time) as "avg_online_num",
  FROM_UNIXTIME(online_statistic_time,'%Y-%m-%d') as "dayTime"
from	
  user_online_count_tbl
where
  FROM_UNIXTIME(online_statistic_time,'%Y-%m-%d') = FROM_UNIXTIME(UNIX_TIMESTAMP(current_date())-24*60*60*10,'%Y-%m-%d')
group by
   FROM_UNIXTIME(online_statistic_time,'%Y-%m-%d')
Copy after login

?

?

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP's big data structure processing skills PHP's big data structure processing skills May 08, 2024 am 10:24 AM

Big data structure processing skills: Chunking: Break down the data set and process it in chunks to reduce memory consumption. Generator: Generate data items one by one without loading the entire data set, suitable for unlimited data sets. Streaming: Read files or query results line by line, suitable for large files or remote data. External storage: For very large data sets, store the data in a database or NoSQL.

How to optimize MySQL query performance in PHP? How to optimize MySQL query performance in PHP? Jun 03, 2024 pm 08:11 PM

MySQL query performance can be optimized by building indexes that reduce lookup time from linear complexity to logarithmic complexity. Use PreparedStatements to prevent SQL injection and improve query performance. Limit query results and reduce the amount of data processed by the server. Optimize join queries, including using appropriate join types, creating indexes, and considering using subqueries. Analyze queries to identify bottlenecks; use caching to reduce database load; optimize PHP code to minimize overhead.

How to use MySQL backup and restore in PHP? How to use MySQL backup and restore in PHP? Jun 03, 2024 pm 12:19 PM

Backing up and restoring a MySQL database in PHP can be achieved by following these steps: Back up the database: Use the mysqldump command to dump the database into a SQL file. Restore database: Use the mysql command to restore the database from SQL files.

How to insert data into a MySQL table using PHP? How to insert data into a MySQL table using PHP? Jun 02, 2024 pm 02:26 PM

How to insert data into MySQL table? Connect to the database: Use mysqli to establish a connection to the database. Prepare the SQL query: Write an INSERT statement to specify the columns and values ​​to be inserted. Execute query: Use the query() method to execute the insertion query. If successful, a confirmation message will be output.

How to fix mysql_native_password not loaded errors on MySQL 8.4 How to fix mysql_native_password not loaded errors on MySQL 8.4 Dec 09, 2024 am 11:42 AM

One of the major changes introduced in MySQL 8.4 (the latest LTS release as of 2024) is that the "MySQL Native Password" plugin is no longer enabled by default. Further, MySQL 9.0 removes this plugin completely. This change affects PHP and other app

Complete collection of excel function formulas Complete collection of excel function formulas May 07, 2024 pm 12:04 PM

1. The SUM function is used to sum the numbers in a column or a group of cells, for example: =SUM(A1:J10). 2. The AVERAGE function is used to calculate the average of the numbers in a column or a group of cells, for example: =AVERAGE(A1:A10). 3. COUNT function, used to count the number of numbers or text in a column or a group of cells, for example: =COUNT(A1:A10) 4. IF function, used to make logical judgments based on specified conditions and return the corresponding result.

How to use MySQL stored procedures in PHP? How to use MySQL stored procedures in PHP? Jun 02, 2024 pm 02:13 PM

To use MySQL stored procedures in PHP: Use PDO or the MySQLi extension to connect to a MySQL database. Prepare the statement to call the stored procedure. Execute the stored procedure. Process the result set (if the stored procedure returns results). Close the database connection.

How to create a MySQL table using PHP? How to create a MySQL table using PHP? Jun 04, 2024 pm 01:57 PM

Creating a MySQL table using PHP requires the following steps: Connect to the database. Create the database if it does not exist. Select a database. Create table. Execute the query. Close the connection.

See all articles