针对customers表的查询操作举例

https://www.bilibili.com/video/BV1eJ411c7rf?p=17

Java与SQL对应数据类型转换表

Java 类型	SQL 类型
boolean	BIT
byte	TINYINT
short	SMALLINT
int	INTEGER
long	BIGINT
String	CHAR, VARCHAR, LONGVARCHAR
byte array	BINARY,，VAR BINARY
java.sql.Date	DATE
java.sql.Time	TIME
java.sql.Timestamp	TIMESTAMP

import io.github.jihch.bean.Customer;
import io.github.jihch.util.JDBCUtils;
import org.junit.Test;

import java.sql.*;

/**
 * 针对于 Customers 表的查询操作
 */
public class CustomerForQuery {

    @Test
    public void testQuery1() {

        String sql = "select id, name, email, birth from customers where id = ?";
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet resultSet = null;

        try {
            conn = JDBCUtils.getConnection();

            ps = conn.prepareStatement(sql);
            ps.setObject(1, 2);

            //执行，并返回结果集
            resultSet = ps.executeQuery();

            //处理结果集
            if (resultSet.next()) { //next():判断结果集的下一条是否有数据，如果有数据返回 true，并指针下移；如果返回 false，指针不会下移

                //获取当前这条数据的各个字段值
                int id = resultSet.getInt(1);
                String name = resultSet.getString(2);
                String email = resultSet.getString(3);
                Date birth = resultSet.getDate(4);

                //方式一：
//            System.out.println("id = " + id+", name = " + name + ", email = " + email + ", birth = " + birth);

                //方式二：
//            Object[] data = new Object[]{id, name, email, birth};

                //方式三：将数据封装为一个对象（推荐）
                Customer customer = new Customer(id, name, email, birth);
                System.out.println(customer);

            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtils.closeResource(conn, ps, resultSet);
        }

    }//end testQuery1

}