Java自学-JDBC 增、删、改

JDBC 增、删、改

CRUD是最常见的数据库操作，即增删改查
C 增加(Create)
R 读取查询(Retrieve)
U 更新(Update)
D 删除(Delete)

在JDBC中增加，删除，修改的操作都很类似，只是传递不同的SQL语句就行了。

步骤 1 : 增加

这段代码就是Hello JDBC中的代码，用于向数据库中插入数据

package jdbc;
   
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
   
public class TestJDBC {
    public static void main(String[] args) {
   
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
   
        try (
            Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8",
                "root", "admin");
            Statement s = c.createStatement();             
        )
        {
            String sql = "insert into hero values(null," + "'提莫'" + "," + 313.0f + "," + 50 + ")";
            s.execute(sql);
               
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

步骤 2 : 删除

删除和增加很类似，只不过是执行的SQL语句不一样罢了

package jdbc;
   
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
   
public class TestJDBC {
    public static void main(String[] args) {
   
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
   
        try (
            Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8",
                "root", "admin");
            Statement s = c.createStatement();             
        )
        {
            String sql = "delete from hero where id = 5";
            s.execute(sql);
               
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

步骤 3 : 修改

修改也一样，执行另一条SQL语句就可以了

package jdbc;
   
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
   
public class TestJDBC {
    public static void main(String[] args) {
   
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
   
        try (
            Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8",
                "root", "admin");
            Statement s = c.createStatement();             
        )
        {
            String sql = "update hero set name = 'name 5' where id = 3";
            s.execute(sql);
               
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

练习： 增、删、改

设计一个方法

public static void execute(String sql)

方法接受的参数是SQL语句，无论是增加，删除，还是修改，都调用这个方法，每次传不同的SQL语句作为参数

答案 :

package jdbc;
 
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
 
public class TestJDBC {
 
    public static void execute(String sql) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
 
        try (Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8",
                "root", "admin"); Statement s = c.createStatement();) {
 
            s.execute(sql);
 
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
 
    public static void main(String[] args) {
        execute("delete from hero where id = 1");
    }
}