数据结构
网络
关系型数据库管理系统
操作系统
Java
MS Excel
iOS
HTML
CSS
安卓
Python
C 编程
C++
C#
MongoDB
MySQL
Javascript
PHP
物理学
化学
生物学
数学
英语
经济学
心理学
社会学
时装研究
法律研究如何在 JDBC 中获取行数？
SQL Count() 函数可返回表中的行数。利用此函数可以获取表中的行数。
select count(*) from TABLE_NAME;
假设我们已通过 Statement 对象与 MySQL 建立连接，并在名为 mydatabase 的数据库中创建了一个表:
//Creating the Statement object
Statement stmt = con.createStatement();
//Query to create a table
String query = "CREATE TABLE Cricketers_Data( "
+ "First_Name VARCHAR(255), "
+ "Last_Name VARCHAR(255), "
+ "Date_Of_Birth Date, "
+ "Place_Of_Birth VARCHAR(255), "
+ "Country VARCHAR(255))";
//Executing the query
stmt.execute(query);
System.out.println("Table created......");接着我们利用 prepared statement 向此表中插入 5 列:
//Query to insert values Query = "INSERT INTO Cricketers_Data values (?, ?, ?, ?, ?)"; PreparedStatement pstmt = con.prepareStatement(query); pstmt.setString(1, "Shikhar"); pstmt.setString(2, "Dhawan"); pstmt.setDate(3, new Date(376401869000L)); pstmt.setString(4, "Delhi"); pstmt.setString(5, "India"); pstmt.executeUpdate(); pstmt.setString(1, "Jonathan"); pstmt.setString(2, "Trott"); pstmt.setDate(3, new Date(356788333000L)); pstmt.setString(4, "CapeTown"); pstmt.setString(5, "SouthAfrica"); pstmt.executeUpdate(); pstmt.setString(1, "Kumara"); pstmt.setString(2, "Sangakkara"); pstmt.setDate(3, new Date(246801133000L)); pstmt.setString(4, "Matale"); pstmt.setString(5, "Srilanka"); pstmt.executeUpdate(); pstmt.setString(1, "Virat"); pstmt.setString(2, "Kohli"); pstmt.setDate(3, new Date(546781933000L)); pstmt.setString(4, "Delhi"); pstmt.setString(5, "India"); pstmt.executeUpdate(); pstmt.setString(1, "Rohit"); pstmt.setString(2, "Sharma"); pstmt.setDate(3, new Date(546781933000L)); pstmt.setString(4, "Nagpur"); pstmt.setString(5, "India"); pstmt.executeUpdate();
这样 Cricketers_Data 表的显示效果如下:
+------------+------------+---------------+----------------+-------------+ | First_Name | Last_Name | Date_Of_Birth | Place_Of_Birth | Country | +------------+------------+---------------+----------------+-------------+ | Shikhar | Dhawan | 1981-12-05 | Delhi | India | | Jonathan | Trott | 1981-04-22 | CapeTown | SouthAfrica | | Kumara | Sangakkara | 1977-10-27 | Matale | Srilanka | | Virat | Kohli | 1987-04-30 | Delhi | India | | Rohit | Sharma | 1987-04-30 | Nagpur | India | +------------+------------+---------------+----------------+-------------+
示例
以下 JDBC 程序建立与 MySQL 的连接，并显示名为 cricketers_data 的表中的行数。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Count_Example {
public static void main(String args[]) throws Exception {
//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 object
Statement stmt = con.createStatement();
//Query to get the number of rows in a table
String query = "select count(*) from Cricketers_Data";
//Executing the query
ResultSet rs = stmt.executeQuery(query);
//Retrieving the result
rs.next();
int count = rs.getInt(1);
System.out.println("Number of records in the cricketers_data table: "+count);
}
}输出
Connection established...... Number of records in the cricketers_data table: 5
更新于: 30-7-2019
6K+ 浏览
广告