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法律研究Java ResultSet next() 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 語句返回的此類表格資料。
即 ResultSet 物件儲存由執行查詢資料庫語句的方法（通常是 Statement 介面的 executeQuery() 方法）返回的表格資料。
ResultSet 物件有一個游標/指標，指向當前行。最初，此游標位於第一行之前。
ResultSet 介面的 next() 方法將當前 (ResultSet) 物件的指標從當前位置移動到下一行。
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from MyPlayers");
rs.next();即，第一次呼叫 next() 方法時，結果集指標/游標將移動到第 1 行（從預設位置）。
第二次呼叫 next() 方法時，結果集游標將移動到第 2 行。
返回值
此方法返回一個布林值，指定 ResultSet 物件是否包含更多行。
如果在其當前位置的下一行沒有行，則此方法返回 false，否則返回 true。
在 while 迴圈中使用此方法，您可以迭代結果集的內容。
while(rs.next()){
System.out.println(rs.getString(1));
System.out.println(rs.getString(2));
}示例
讓我們使用如下所示的 CREATE 語句在MySQL 資料庫中建立一個名為 MyPlayers 的表：
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');以下 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，使用 next() 方法將游標移動到下一行三次，並在每個位置列印該行內容。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class ResultSet_next {
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);
System.out.println("Contents of the first record: ");
//Moving the cursor from default position to 1st row.
rs.next();
//Current record details.
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();
//Moving the cursor from default position to 1st row.
rs.next();
//Current record details.
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();
//Moving the cursor from 1st row position to 2nd row.
rs.next();
//Current record details.
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();
//Moving the cursor from 2nd row to 3rd row.
rs.next();
//Current record details.
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 first record: ID: 1, Name: Shikhar, Age: Dhawan, Salary: 1981-12-05, Address: DelhiAddress: India ID: 2, Name: Jonathan, Age: Trott, Salary: 1981-04-22, Address: CapeTownAddress: SouthAfrica ID: 3, Name: Kumara, Age: Sangakkara, Salary: 1977-10-27, Address: MataleAddress: Srilanka ID: 4, Name: Virat, Age: Kohli, Salary: 1988-11-05, Address: MumbaiAddress: India
更新於: 2024-05-31
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