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法律研究Java ResultSet next() 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 语句返回的此类表格数据。
即 ResultSet 对象保存由执行查询数据库语句的方法（通常是 Statement 接口的 executeQuery() 方法）返回的表格数据。
ResultSet 对象有一个光标/指针，指向当前行。最初，此光标位于第一行之前。
ResultSet 接口的 next() 方法将当前 (ResultSet) 对象的指针从当前位置移动到下一行。
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from MyPlayers");
rs.next();即，第一次调用 next() 方法时，结果集指针/光标将移动到第 1 行（从默认位置）。
第二次调用 next() 方法时，结果集光标将移动到第 2 行。
返回值
此方法返回一个布尔值，指定 ResultSet 对象是否包含更多行。
如果在其当前位置的下一行没有行，则此方法返回 false，否则返回 true。
在 while 循环中使用此方法，您可以迭代结果集的内容。
while(rs.next()){
System.out.println(rs.getString(1));
System.out.println(rs.getString(2));
}示例
让我们使用如下所示的 CREATE 语句在MySQL 数据库中创建一个名为 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) );
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');以下 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，使用 next() 方法将光标移动到下一行三次，并在每个位置打印该行内容。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class ResultSet_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://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);
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();
}
}输出
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
更新于: 2024-05-31
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