jdbc驱动到官网下载,放在jdk的相关目录下面,或者jar文件加入到工程下面 package test_mysql;import java.sql.*;import java.util.Set;public class testjdbc {public static Connection getConnection() throws ClassNotFoundException, SQLException{Stri
jdbc驱动到官网下载,放在jdk的相关目录下面,或者jar文件加入到工程下面
package test_mysql; import java.sql.*; import java.util.Set; public class testjdbc { public static Connection getConnection() throws ClassNotFoundException, SQLException{ String URL="jdbc:mysql://localhost:3306/employees"; //加载驱动程序 Class.forName("com.mysql.jdbc.Driver"); String user="root"; String passwd=""; //默认密码为空 //还有选择数据库,哪个数据 //DriverManager. //Connection con=DriverManager.getConnection(URL, user, passwd); //Connection con=DriverManager.getConnection(url, user, password); String test_url=""; //String my_url="jdbc:mysql://localhost:3306;DatabaseName=employees;User=root;Password="; //test_url+=URL+3306+";"+"DatabaseName=employees;"+"User=root;"+"Password="+""; Connection con=DriverManager.getConnection(URL,user,passwd); return con; } public static void main(String[] args){ String sql="select * from departments"; Statement statement=null; Connection con=null; ResultSet set=null; try { con = getConnection(); //con.set if(con==null) System.out.println("con null"); statement=con.createStatement(); set=statement.executeQuery(sql); //int n=set.getFetchSize(); //System.out.println(n); while(set.next()){ System.out.println(set.getString(1)+" "+set.getString(2)); } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ if(con!=null) try { set.close(); statement.close(); con.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }
更多相关教程请访问 MySQL视频教程

MySQLoffersvariousstorageengines,eachsuitedfordifferentusecases:1)InnoDBisidealforapplicationsneedingACIDcomplianceandhighconcurrency,supportingtransactionsandforeignkeys.2)MyISAMisbestforread-heavyworkloads,lackingtransactionsupport.3)Memoryengineis

Common security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.

Identifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.

To monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.

The main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.


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