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法學Java ResultSet last() 方法及示例
當我們執行某些SQL查詢（通常是SELECT查詢）時，它們會返回表格資料。
java.sql.ResultSet 介面表示SQL語句返回的這種表格資料。
即ResultSet物件儲存由執行查詢資料庫語句（通常是Statement介面的executeQuery()方法）返回的表格資料。
ResultSet物件有一個遊標/指標，指向當前行。最初，此遊標位於第一行之前。
last() 方法是ResultSet介面的方法，它將當前(ResultSet)物件的指標從當前位置移動到最後一行。
此方法返回一個布林值，指定ResultSet遊標是否位於有效行上。如果ResultSet物件中沒有行，則此方法返回false，否則返回true。
示例
讓我們使用CREATE語句在MySQL資料庫中建立一個名為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) );
現在，我們將使用INSERT語句在MyPlayers表中插入7條記錄：
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程式建立與資料庫的連線，將表MyPlayers的內容檢索到ResultSet物件中，列印其內容，並使用last()方法列印結果的最後一行內容。
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:///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();
}
}輸出
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
更新於：2019年7月30日
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