今天完成的任务

了解了关于sql的其它关键字

idbc中对数据库的操作均通过以下代码语句输入

Statement stmt = null;

stmt = conn.createStatement();

stmt.executeUpdate(sql);

sql即需要输入的语句

1）CREATE DATABASE 创建一个新数据库

2）DROP DATABASE删除一个数据库

3）CREATE TABLE table_name

(   column_name    column_data_type, 

    column_name    column_data_type,

    column_name    column_data_type   ...);
范例

 CREATE TABLE Employees(
   id INT NOT NULL,
   age INT NOT NULL,
   first VARCHAR(255),
   last VARCHAR(255),
   PRIMARY KEY ( id ));

4）DROP TABLE table_name;删除表

5）INSERT INTO table_name VALUES (column1, column2, ...);插入一行新数据

6）SELECT column_name, column_name, ...  

FROM table_name

WHERE conditions;

在名为table_name的表中读取名为conditions关键字的，column_name列数据

（WHERE后可以使用比较运算符）

7）UPDATE table_name    

SET column_name = value, column_name = value, ...   

WHERE conditions;

在名为table_name的表中将名为conditions关键字的，column_name列数据替换为输入值

（WHERE后可以使用比较运算符）

2.以下为今天写的

//STEP 1. Import required packages
// See more detail at http://www.yiibai.com/jdbc/

import java.sql.*;

public class InsertRecords {
    // JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost:3306/EMP?";

    //  Database credentials
    static final String USER = "root";
    static final String PASS = "123";

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try{
            //STEP 2: Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            //STEP 3: Open a connection
            System.out.println("Connecting to a selected database...");
            conn = DriverManager.getConnection(DB_URL, USER, PASS);
            System.out.println("Connected database successfully...");

            //STEP 4: Execute a query
            System.out.println("Inserting records into the table...");
            stmt = conn.createStatement();

            String sql = "INSERT INTO employees " +
                    "VALUES (100, '4', 'Li', 18)";
            stmt.executeUpdate(sql);
            sql = "INSERT INTO employees " +
                    "VALUES (101, '3', 'Py', 25)";
            stmt.executeUpdate(sql);
            sql = "INSERT INTO employees " +
                    "VALUES (102, '2', 'Ru', 30)";
            stmt.executeUpdate(sql);
            sql = "INSERT INTO employees " +
                    "VALUES(103, '1', 'Ja', 28)";
            stmt.executeUpdate(sql);
            System.out.println("Inserted records into the table...");

        }catch(SQLException se){
            //Handle errors for JDBC
            se.printStackTrace();
        }catch(Exception e){
            //Handle errors for Class.forName
            e.printStackTrace();
        }finally{
            //finally block used to close resources
            try{
                if(stmt!=null)
                    conn.close();
            }catch(SQLException se){
            }// do nothing
            try{
                if(conn!=null)
                    conn.close();
            }catch(SQLException se){
                se.printStackTrace();
            }//end finally try
        }//end try
        System.out.println("Goodbye!");
    }//end main
}//end JDBCExample

现在有一个小问题，也就是如果我使用两个不同的sql语句导入同一个stmt.executeUpdate(sql);里面

stmt = conn.createStatement();//对 Statement执行sql语句，其实就是对这个执行的。。

String sql;
sql = "SELECT id, first, last, age FROM Employees";//查询数据的语法
ResultSet rs = stmt.executeQuery(sql);//把查询到的数值导入一个数组
sql = "INSERT INTO employees " + "VALUES (1770, '11', 'Li', 180)";
stmt.executeUpdate(sql);

会报java.sql.SQLException: Operation not allowed after ResultSet closed

但是

String sql = "INSERT INTO employees " +
        "VALUES (100, '4', 'Li', 18)";
stmt.executeUpdate(sql);
sql = "INSERT INTO employees " +
        "VALUES (101, '3', 'Py', 25)";
stmt.executeUpdate(sql);
sql = "INSERT INTO employees " +
        "VALUES (102, '2', 'Ru', 30)";
stmt.executeUpdate(sql);
sql = "INSERT INTO employees " +
        "VALUES(103, '1', 'Ja', 28)";
stmt.executeUpdate(sql);

如果不写查询语句这样写就不会报错

不知道因为什么...

明天要做的事

听从师兄的建议，补习java基础，暂时放置任务1后面的内容

遇到的问题

如上

收获

1.对后面的学习计划更加的了解

2.掌握了sql的基本语法