如何用Java實現獲得MySQL數據庫中所有表的記錄總數

在MySQL中，可以通過SELECT COUNT(*) FROM table_name查詢某個表中有多少條記錄。如果想知道某個數據庫中所有別的記錄總數應該怎麼做呢？本文給出兩種可行的Java程序，解決該問題。
 
1. 首先確定數據庫中有多少個表，然後對每個表執行SELECT COUNT(*) FROM table_name

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class Test {
 private static String driver = "com.mysql.jdbc.Driver";
 private static String url = "jdbc:mysql://127.0.0.1/";
 private static String db = "test";
 private static String user = "root";
 private static String pass = "test";

 static Connection conn = null;
 static Statement statement = null;
 static PreparedStatement ps = null;
 static ResultSet rs = null;
 
 static List<String> tables = new ArrayList<String>();
 
 public static void startMySQLConn() {
  try {
   Class.forName(driver).newInstance();
   conn = DriverManager.getConnection(url+db, user, pass);
   if (!conn.isClosed()) {
    System.out.println("Succeeded connecting to MySQL!");
   }
   
   statement = conn.createStatement();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 public static void closeMySQLConn() {
  if(conn != null){
   try {
    conn.close();
    System.out.println("Database connection terminated!");
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }
 
 public static void getTables() {
  String sql = "show tables;";
  try {
   ps = conn.prepareStatement(sql);
   rs = ps.executeQuery();
   while (rs.next()) {
    tables.add(rs.getString(1));
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 public static long getDbSum() {
  long sum = 0;
  String sql = "select count(*) from ";
  try {
   for(String tblName: tables) {
    ps = conn.prepareStatement(sql + tblName + ";");
    rs = ps.executeQuery();
    while (rs.next()) {
     sum += rs.getInt(1);
    }
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
  return sum;
 }
 
 public static void main(String[] args) {
  startMySQLConn();
  getTables();
  System.out.println(getDbSum());
  closeMySQLConn();
 }
}

2. 借助information_schema庫的tables表

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class Test {
 private static String driver = "com.mysql.jdbc.Driver";
 private static String url = "jdbc:mysql://127.0.0.1/";
 private static String db = "test";
 private static String user = "root";
 private static String pass = "test";

 static Connection conn = null;
 static Statement statement = null;
 static PreparedStatement ps = null;
 static ResultSet rs = null;
 
 public static void startMySQLConn() {
  try {
   Class.forName(driver).newInstance();
   conn = DriverManager.getConnection(url+db, user, pass);
   if (!conn.isClosed()) {
    System.out.println("Succeeded connecting to MySQL!");
   }
   
   statement = conn.createStatement();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 public static void closeMySQLConn() {
  if(conn != null){
   try {
    conn.close();
    System.out.println("Database connection terminated!");
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }
 
 public static void useDB() {
  String sql = "use information_schema;";
  try {
   ps = conn.prepareStatement(sql);
   rs = ps.executeQuery();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 public static long getDbSum() {
  long sum = 0;
  String sql = "select table_name,table_rows from tables where TABLE_SCHEMA = '" +
    db + "' order by table_rows desc;";
  //System.out.println(sql);
  try {
   ps = conn.prepareStatement(sql);
   rs = ps.executeQuery();
   while (rs.next()) {
    sum += rs.getInt(2);
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
  return sum;
 }
 
 public static void main(String[] args) {
  startMySQLConn();
  useDB();
  System.out.println(getDbSum());
  closeMySQLConn();
 }
}