0318

execute()几乎可以执行任何SQL语句，比较麻烦但是不清楚语句类型时可以用它。
PreparedStatement预编译SQL：
执行效率比statement高，降低变编程杂程度，且可以防止SQL注入。其中占位符只能代替普通值。

import java.util.*;
import java.io.*;
import java.sql.*;
public class ExecuteSQL
{
	private String driver;
	private String url;
	private String user;
	private String pass;
	public void initParam(String paramFile)throws Exception
	{
		Properties props = new Properties();
		props.load(new FileInputStream(paramFile));
		driver = props.getProperty("driver");
		url = props.getProperty("url");
		user = props.getProperty("user");
		pass = props.getProperty("pass");
	}
	public void executeSql(String sql)throws Exception
	{
		Class.forName(driver);
		try(
			Connection conn = DriverManager.getConnection(url, user , pass);
			Statement stmt = conn.createStatement())
		{
			// 执行SQL,返回boolean值表示是否包含ResultSet
			boolean hasResultSet = stmt.execute(sql);
			// 如果执行后有ResultSet结果集,则表明是查询语句
			if (hasResultSet)
			{
				try(
					// 获取结果集
					ResultSet rs = stmt.getResultSet())
				{
					// ResultSetMetaData是用于分析结果集的元数据接口
					ResultSetMetaData rsmd = rs.getMetaData();
					int columnCount = rsmd.getColumnCount();
					// 迭代输出ResultSet对象
					while (rs.next())
					{
						// 依次输出每列的值
						for (int i = 0 ; i < columnCount ; i++ )
						{
							System.out.print(rs.getString(i + 1) + "\t");
						}
						System.out.print("\n");
					}
				}
			}
			else
			{
				System.out.println("该SQL语句影响的记录有"
					+ stmt.getUpdateCount() + "条");
			}
		}
	}
	public static void main(String[] args) throws Exception
	{
		ExecuteSQL es = new ExecuteSQL();
		es.initParam("mysql.ini");
		System.out.println("------执行删除表的DDL语句-----");
		es.executeSql("drop table if exists my_test");
		System.out.println("------执行建表的DDL语句-----");
		es.executeSql("create table my_test"
			+ "(test_id int auto_increment primary key, "
			+ "test_name varchar(255))");
		System.out.println("------执行插入数据的DML语句-----");
		es.executeSql("insert into my_test(test_name) "
			+ "select student_name from student_table");
		System.out.println("------执行查询数据的查询语句-----");
		es.executeSql("select * from my_test");
	}
}