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法学Java ResultSet last() 方法及示例
当我们执行某些SQL查询（通常是SELECT查询）时，它们会返回表格数据。
java.sql.ResultSet 接口表示SQL语句返回的这种表格数据。
即ResultSet对象保存由执行查询数据库语句（通常是Statement接口的executeQuery()方法）返回的表格数据。
ResultSet对象有一个游标/指针，指向当前行。最初，此游标位于第一行之前。
last() 方法是ResultSet接口的方法，它将当前(ResultSet)对象的指针从当前位置移动到最后一行。
此方法返回一个布尔值，指定ResultSet游标是否位于有效行上。如果ResultSet对象中没有行，则此方法返回false，否则返回true。
示例
让我们使用CREATE语句在MySQL数据库中创建一个名为MyPlayers的表，如下所示：
CREATE TABLE MyPlayers( ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Date_Of_Birth date, Place_Of_Birth VARCHAR(255), Country VARCHAR(255), PRIMARY KEY (ID) );
现在，我们将使用INSERT语句在MyPlayers表中插入7条记录：
insert into MyPlayers values(1, 'Shikhar', 'Dhawan', DATE('1981-12-05'), 'Delhi', 'India');
insert into MyPlayers values(2, 'Jonathan', 'Trott', DATE('1981-04-22'), 'CapeTown', 'SouthAfrica');
insert into MyPlayers values(3, 'Kumara', 'Sangakkara', DATE('1977-10-27'), 'Matale', 'Srilanka');
insert into MyPlayers values(4, 'Virat', 'Kohli', DATE('1988-11-05'), 'Delhi', 'India');
insert into MyPlayers values(5, 'Rohit', 'Sharma', DATE('1987-04-30'), 'Nagpur', 'India');
insert into MyPlayers values(6, 'Ravindra', 'Jadeja', DATE('1988-12-06'), 'Nagpur', 'India');
insert into MyPlayers values(7, 'James', 'Anderson', DATE('1982-06-30'), 'Burnley', 'England');下面的JDBC程序建立与数据库的连接，将表MyPlayers的内容检索到ResultSet对象中，打印其内容，并使用last()方法打印结果的最后一行内容。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class ResultSet_last {
public static void main(String args[]) throws SQLException {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String mysqlUrl = "jdbc:mysql://127.0.0.1/mydatabase";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//Creating the Statement
Statement stmt = con.createStatement();
//Query to retrieve records
String query = "Select * from MyPlayers";
//Executing the query
ResultSet rs = stmt.executeQuery(query);
//Moving cursor to the Last position in the ResultSet.
rs.last();
System.out.println("Printing the contents of the current row: ");
System.out.print("ID: "+rs.getInt("ID")+", ");
System.out.print("Name: "+rs.getString("First_Name")+", ");
System.out.print("Age: "+rs.getString("Last_Name")+", ");
System.out.print("Salary: "+rs.getDate("Date_Of_Birth")+", ");
System.out.print("Country: "+rs.getString("Place_Of_Birth")+", ");
System.out.print("Address: "+rs.getString("Country"));
System.out.println();
}
}输出
Connection established...... Contents of the MyPlayers table: ID: 1, Name: Shikhar, Age: Dhawan, Salary: 1981-12-05, Country: Delhi, Address: India ID: 2, Name: Jonathan, Age: Trott, Salary: 1981-04-22, Country: CapeTown, Address: SouthAfrica ID: 3, Name: Kumara, Age: Sangakkara, Salary: 1977-10-27, Country: Matale, Address: Srilanka ID: 4, Name: Virat, Age: Kohli, Salary: 1988-11-05, Country: Mumbai, Address: India ID: 5, Name: Rohit, Age: Sharma, Salary: 1987-04-30, Country: Nagpur, Address: India ID: 6, Name: Ravindra, Age: Jadeja, Salary: 1988-12-06, Country: Nagpur, Address: India ID: 7, Name: James, Age: Anderson, Salary: 1982-06-30, Country: Burnley , Address: England ID: 8, Name: Ryan, Age: McLaren, Salary: 1983-02-09, Country: Kumberly, Address: null Printing the contents of the last row: ID: 8, Name: Ryan, Age: McLaren, Salary: 1983-02-09, Country: Kumberly, Address: null
更新于：2019年7月30日
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