选择MySQL数据库进行连接的简单示例_MySQL
一旦获得MySQL服务器的连接，需要选择一个特定的数据库工作。这是因为MySQL服务器可能有一个以上的数据库。
从命令提示符，选择MySQL数据库：
这是很简单的选择一个特定的数据库mysql>提示符。选择一个特定的数据库，可以使用SQL命令。
例子:
下面是一个例子，选择数据库称为 TUTORIALS:
[root@host]# mysql -u root -p Enter password:****** mysql> use TUTORIALS; Database changed mysql>
现在已经选择教程数据库教程数据库和所有的后续操作都将进行。
注: 所有的数据库名，表名，表中的字段名称是区分大小写的。所以将不得不使用prpoer名字，而给予任何SQL命令。
使用PHP脚本选择MySQL数据库：
PHP提供了函数mysql_select_db选择一个数据库。成功返回TRUE，否则返回FALSE。
语法:
bool mysql_select_db( db_name, connection );
例子:
下面是这个例子展示如何选择一个数据库。
<html>
<head>
<title>Selecting MySQL Database - by www.jb51.com</title>
</head>
<body>
<?php
$dbhost = 'localhost:3036';
$dbuser = 'guest';
$dbpass = 'guest123';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
die('Could not connect: ' . mysql_error());
}
echo 'Connected successfully';
mysql_select_db( 'TUTORIALS' );
mysql_close($conn);
?>
</body>
</html>
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
AI Hentai Generator
Generate AI Hentai for free.
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
1374
52
The relationship between mysql user and database
Apr 08, 2025 pm 07:15 PM
In MySQL database, the relationship between the user and the database is defined by permissions and tables. The user has a username and password to access the database. Permissions are granted through the GRANT command, while the table is created by the CREATE TABLE command. To establish a relationship between a user and a database, you need to create a database, create a user, and then grant permissions.
RDS MySQL integration with Redshift zero ETL
Apr 08, 2025 pm 07:06 PM
Data Integration Simplification: AmazonRDSMySQL and Redshift's zero ETL integration Efficient data integration is at the heart of a data-driven organization. Traditional ETL (extract, convert, load) processes are complex and time-consuming, especially when integrating databases (such as AmazonRDSMySQL) with data warehouses (such as Redshift). However, AWS provides zero ETL integration solutions that have completely changed this situation, providing a simplified, near-real-time solution for data migration from RDSMySQL to Redshift. This article will dive into RDSMySQL zero ETL integration with Redshift, explaining how it works and the advantages it brings to data engineers and developers.
Do mysql need to pay
Apr 08, 2025 pm 05:36 PM
MySQL has a free community version and a paid enterprise version. The community version can be used and modified for free, but the support is limited and is suitable for applications with low stability requirements and strong technical capabilities. The Enterprise Edition provides comprehensive commercial support for applications that require a stable, reliable, high-performance database and willing to pay for support. Factors considered when choosing a version include application criticality, budgeting, and technical skills. There is no perfect option, only the most suitable option, and you need to choose carefully according to the specific situation.
Query optimization in MySQL is essential for improving database performance, especially when dealing with large data sets
Apr 08, 2025 pm 07:12 PM
1. Use the correct index to speed up data retrieval by reducing the amount of data scanned select*frommployeeswherelast_name='smith'; if you look up a column of a table multiple times, create an index for that column. If you or your app needs data from multiple columns according to the criteria, create a composite index 2. Avoid select * only those required columns, if you select all unwanted columns, this will only consume more server memory and cause the server to slow down at high load or frequency times For example, your table contains columns such as created_at and updated_at and timestamps, and then avoid selecting * because they do not require inefficient query se
How to optimize MySQL performance for high-load applications?
Apr 08, 2025 pm 06:03 PM
MySQL database performance optimization guide In resource-intensive applications, MySQL database plays a crucial role and is responsible for managing massive transactions. However, as the scale of application expands, database performance bottlenecks often become a constraint. This article will explore a series of effective MySQL performance optimization strategies to ensure that your application remains efficient and responsive under high loads. We will combine actual cases to explain in-depth key technologies such as indexing, query optimization, database design and caching. 1. Database architecture design and optimized database architecture is the cornerstone of MySQL performance optimization. Here are some core principles: Selecting the right data type and selecting the smallest data type that meets the needs can not only save storage space, but also improve data processing speed.
Understand ACID properties: The pillars of a reliable database
Apr 08, 2025 pm 06:33 PM
Detailed explanation of database ACID attributes ACID attributes are a set of rules to ensure the reliability and consistency of database transactions. They define how database systems handle transactions, and ensure data integrity and accuracy even in case of system crashes, power interruptions, or multiple users concurrent access. ACID Attribute Overview Atomicity: A transaction is regarded as an indivisible unit. Any part fails, the entire transaction is rolled back, and the database does not retain any changes. For example, if a bank transfer is deducted from one account but not increased to another, the entire operation is revoked. begintransaction; updateaccountssetbalance=balance-100wh
How to fill in mysql username and password
Apr 08, 2025 pm 07:09 PM
To fill in the MySQL username and password: 1. Determine the username and password; 2. Connect to the database; 3. Use the username and password to execute queries and commands.
MySQL: The Ease of Data Management for Beginners
Apr 09, 2025 am 12:07 AM
MySQL is suitable for beginners because it is simple to install, powerful and easy to manage data. 1. Simple installation and configuration, suitable for a variety of operating systems. 2. Support basic operations such as creating databases and tables, inserting, querying, updating and deleting data. 3. Provide advanced functions such as JOIN operations and subqueries. 4. Performance can be improved through indexing, query optimization and table partitioning. 5. Support backup, recovery and security measures to ensure data security and consistency.
