Java自學-JDBC 增、刪、改

JDBC 增、刪、改

CRUD是最多見的數據庫操做，即增刪改查 C 增長(Create) R 讀取查詢(Retrieve) U 更新(Update) D 刪除(Delete)

在JDBC中增長，刪除，修改的操做都很相似，只是傳遞不一樣的SQL語句就好了。

步驟 1 : 增長

這段代碼就是Hello JDBC中的代碼，用於向數據庫中插入數據

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();
        }
    }
}

步驟 2 : 刪除

刪除和增長很相似，只不過是執行的SQL語句不同罷了

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();
        }
    }
}

步驟 3 : 修改

修改也同樣，執行另外一條SQL語句就能夠了

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();
        }
    }
}

練習： 增、刪、改

設計一個方法

public static void execute(String sql)

方法接受的參數是SQL語句，不管是增長，刪除，仍是修改，都調用這個方法，每次傳不一樣的SQL語句做爲參數

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");
    }
}