Commonly used mysql date functions
Because I am about to graduate, I have been to several companies for interviews, including one interview for PHP development. Youdao sql has optimization questions. At that time, I was interested in mysql ’s function has not been studied and studied systematically, embarrassing. . .
mysql has the main built-in functions as follows:
NOW()
Returns the current date and time
CURDATE()
Returns the current The date
CURTIME()
Returns the current time
DATE()
Extracts the date or date/time The date part of the expression
EXTRACT()
Return the individual parts of the date/time
DATE_ADD()
Add the specified time interval to the date
DATE_SUB()
Subtract the specified time interval from the date
DATEDIFF()
Returns the number of days between two dates
DATE_FORMAT()
Display date/time in different formats
Also includes some partial functions that return dates :
Select various parts of date and time: date, time, year, quarter, month, day, hour, minute, second, microsecond
set @dt = '2008-09-10 07:15 :30.123456';
select date(@dt); -- 2008-09-10
select time(@dt); -- 07:15:30.123456
select year(@dt) ; -- 2008
select quarter(@dt); -- 3
select month(@dt); -- 9
select week(@dt); -- 36
select day(@ dt); -- 10
select hour(@dt); -- 7
select minute(@dt); -- 15
select second(@dt); -- 30
select microsecond (@dt); -- 123456
These functions are very helpful for comparing dates. Many novices are not very good at handling date functions and are prone to errors. Here is an example:
If there is The table product has a field add_time, and its data type is datetime. Someone may write sql like this:
select * from product where add_time = '2013-01-12'
For this This statement, if the format you store is YY-mm-dd, then OK, if the format you store is: 2013-01-12 23:23:56, you will be in tragedy, this is what you will do You can use the DATE() function to return the date part, so this sql should be processed as follows:
select * from product where Date(add_time) = '2013-01-12'
Here is another one, if you want How about the products added in January 2013?
select * from product where date(add_time) between '2013-01-01' and '2013-01-31'
You can also write like this:
select * from product where Year(add_time) = 2013 and Month(add_time) = 1
You should know the role of mysql date function in dealing with date comparison problems, right?
The above is the detailed content of Commonly used mysql date functions. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
MySQL: An Introduction to the World's Most Popular Database
Apr 12, 2025 am 12:18 AM
MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.
MySQL's Place: Databases and Programming
Apr 13, 2025 am 12:18 AM
MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen
How to connect to the database of apache
Apr 13, 2025 pm 01:03 PM
Apache connects to a database requires the following steps: Install the database driver. Configure the web.xml file to create a connection pool. Create a JDBC data source and specify the connection settings. Use the JDBC API to access the database from Java code, including getting connections, creating statements, binding parameters, executing queries or updates, and processing results.
Why Use MySQL? Benefits and Advantages
Apr 12, 2025 am 12:17 AM
MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.
How to start mysql by docker
Apr 15, 2025 pm 12:09 PM
The process of starting MySQL in Docker consists of the following steps: Pull the MySQL image to create and start the container, set the root user password, and map the port verification connection Create the database and the user grants all permissions to the database
MySQL's Role: Databases in Web Applications
Apr 17, 2025 am 12:23 AM
The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.
Laravel Introduction Example
Apr 18, 2025 pm 12:45 PM
Laravel is a PHP framework for easy building of web applications. It provides a range of powerful features including: Installation: Install the Laravel CLI globally with Composer and create applications in the project directory. Routing: Define the relationship between the URL and the handler in routes/web.php. View: Create a view in resources/views to render the application's interface. Database Integration: Provides out-of-the-box integration with databases such as MySQL and uses migration to create and modify tables. Model and Controller: The model represents the database entity and the controller processes HTTP requests.
How to install mysql in centos7
Apr 14, 2025 pm 08:30 PM
The key to installing MySQL elegantly is to add the official MySQL repository. The specific steps are as follows: Download the MySQL official GPG key to prevent phishing attacks. Add MySQL repository file: rpm -Uvh https://dev.mysql.com/get/mysql80-community-release-el7-3.noarch.rpm Update yum repository cache: yum update installation MySQL: yum install mysql-server startup MySQL service: systemctl start mysqld set up booting
