java操作数据库(JDBC)(优化前)

1.加载驱动 Class.forName("com.mysql.jdbc.Driver")

2.连接数据库(connection conn = DriverManager.getConnection())

3.预执行(创建statement,执行sql语句)
//statement stmt = conn.createStatement()
prepareStatement ps = conn.prepareStatement()

4.执行(查看结果)
ResultSet rs = stmt.executeQuery(excuteUpdate)(sql)

5.释放资源
rs.close()

ps.close()
//stmt.close()
conn.close()

删除操作：

 1 package cn.bdqn;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.PreparedStatement;
 6 import java.sql.SQLException;
 7 
 8 public class Jdbc_test02 {
 9     public static void main(String[] args) {
10         Connection conn = null;
11         PreparedStatement ps = null;
12         int rs = 0;
13         //加载驱动
14         try {
15             Class.forName("com.mysql.jdbc.Driver");
16         //连接数据库
17             String url = "jdbc:mysql://localhost:3306/test2";
18             conn = DriverManager.getConnection(url, "root", "123456");
19         //预连接(执行sql语句)
20             //删除操作
21             String sql = "DELETE from student where sno = 108";
22             ps = conn.prepareStatement(sql);
23         //执行(查看结果)
24             rs = ps.executeUpdate();
25             if(rs > 0) {
26                 System.out.println("删除成功");
27             }else {
28                 System.out.println("删除失败");
29             }
30         } catch (ClassNotFoundException e) {
31             e.printStackTrace();
32         } catch (SQLException e) {
33             e.printStackTrace();
34         } finally {
35             try {
36                 //释放资源
37                 if(ps != null) {
38                     ps.close();
39                 }
40                 if(conn != null){
41                     conn.close();
42                 }
43             } catch (SQLException e) {
44                 e.printStackTrace();
45             }
46         }
47     }
48 }

查询操作：

 1 package cn.bdqn;
 2 
 3 import java.sql.Connection;
 4 import java.sql.DriverManager;
 5 import java.sql.PreparedStatement;
 6 import java.sql.ResultSet;
 7 import java.sql.SQLException;
 8 
 9 public class Jdbc_test05 {
10     public static void main(String[] args) {
11         //1.加载驱动 Class.forName("com.mysql.jdbc.Driver")
12         
13         //2.连接数据库(connection conn = DriverManager.getConnection())
14         
15         //3.预执行(创建statement,执行sql语句)
16         //statement stmt = conn.createStatement()
17         //prepareStatement ps = conn.prepareStatement()
18         
19         //4.执行(查看结果)
20         //ResultSet rs = stmt.executeQuery(excuteUpdate)(sql)
21         //循环遍历
22         
23         //5.释放资源
24         //rs.close()
25         //stmt.close()
26         //conn.close()
27         
28         
29         Connection conn = null;
30         PreparedStatement ps = null;
31         ResultSet rs = null;
32         //1.加载驱动 Class.forName("com.mysql.jdbc.Driver")
33         try {
34             Class.forName("com.mysql.jdbc.Driver");
35         //2.连接数据库(connection conn = DriverManager.getConnection())
36             String url = "jdbc:mysql://localhost:3306/test2";
37             conn = DriverManager.getConnection(url, "root", "123456");
38         //3.预执行(创建statement,执行sql语句)
39             String sql = "SELECT sno,sname,Sbirthday,class from student";
40             ps = conn.prepareStatement(sql);
41         //4.执行(查看结果)
42             rs = ps.executeQuery();
43             while(rs.next()) {
44                 System.out.println(rs.getInt("sno")+"	"+rs.getString("sname")+"	"+rs.getDate("Sbirthday")+"	"+rs.getInt("class"));
45             }
46         } catch (ClassNotFoundException e) {
47             e.printStackTrace();
48         } catch (SQLException e) {
49             e.printStackTrace();
50         } finally {
51                 try {
52                     //释放资源
　　　　　　　　　　　　　　if(rs != null){
　　　　　　　　　　　　　　　　rs.close();
　　　　　　　　　　　　　　}

53                     if(ps != null) {
54                         ps.close();
55                     }
56                     if(conn != null) {
57                     conn.close();
58                     }
59                 } catch (SQLException e) {
60                     e.printStackTrace();
61             }
62         }
63     }
64 }

对于增，删，改操作 int rs = ps.executeUpdate(sql);

查询操作 resultSet rs = ps.executeQuery();