ResultSetMetaData rsmd = pstmt.getMetaData();

DatabaseMetaData dmd = conn.getMetaData();
ResultSet rs = dmd.getPrimaryKeys(null, null, “user”);

17.13.1 DatabaseMetaData

【例17.31】使用DatabaseMetaData取得数据库的元信息

package file;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Savepoint;
import java.text.SimpleDateFormat;

public class demo 
{
	public static final String DBDRIVER = "com.mysql.cj.jdbc.Driver";
	public static final String DBURL = "jdbc:mysql://localhost:3306/java_mysql";
	public static final String DBUSER = "root";
	public static final String DBPASS = "dyh20011022";
	
	public static void main(String[] args) throws Exception
	{		
		Class.forName(DBDRIVER);//驱动
	
		
		Connection conn =DriverManager.getConnection(DBURL, DBUSER, DBPASS);
		DatabaseMetaData dmd = conn.getMetaData();
		ResultSet rs = dmd.getPrimaryKeys(null, null, "user");
		
		
		System.out.println("数据库名称："+dmd.getDatabaseProductName());
		System.out.println("数据库版本："+dmd.getDatabaseMajorVersion()+"."+dmd.getDatabaseMinorVersion());
		while(rs.next())//主键不只一个
		{
			System.out.println("表类别："+rs.getString(1));
			System.out.println("表模式："+rs.getString(2));
			System.out.println("表名称："+rs.getString(3));
			System.out.println("列名称："+rs.getString(4));
			System.out.println("主键序列号："+rs.getString(5));
			System.out.println("主键名称："+rs.getString(6));
			System.out.println("-----------------------");
		}

		//关闭
		conn.close();
	}
}

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因为：多个数据库存在user表
ResultSet rs = dmd.getPrimaryKeys(null, null, “user”);//没有限制具体

17.13.2 ResultSetMetaData

【例 17.32 】取得 ResultSet 的 MetaData

String sql = "select id,name,password,age,sex,birthday from user";
ResultSetMetaData rsmd = pstmt.getMetaData();

rsmd.getColumnCount()
rsmd.isAutoIncrement(1))			
rsmd.getColumnName(1)
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package file;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Savepoint;
import java.text.SimpleDateFormat;
import  java.sql.ResultSetMetaData;

public class demo 
{
	public static final String DBDRIVER = "com.mysql.cj.jdbc.Driver";
	public static final String DBURL = "jdbc:mysql://localhost:3306/java_mysql";
	public static final String DBUSER = "root";
	public static final String DBPASS = "dyh20011022";
	
	public static void main(String[] args) throws Exception
	{		
		Class.forName(DBDRIVER);//驱动
		String sql = "select id,name,password,age,sex,birthday from user";
		
		Connection conn =DriverManager.getConnection(DBURL, DBUSER, DBPASS);
		PreparedStatement pstmt  = conn.prepareStatement(sql);
		ResultSetMetaData rsmd = pstmt.getMetaData();
		
		System.out.println("一共："+rsmd.getColumnCount()+"条信息.");
		if(rsmd.isAutoIncrement(1))
		{
			System.out.println(rsmd.getColumnName(1)+"列自增。");
		}
		
		//关闭
		pstmt.close();
		conn.close();
	}
}

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