为什么一直跳主键报错 299999是最大值吗？主键是没数据的

package com.imooc.jdbc.sample;

import com.imooc.jdbc.hrapp.common.DbUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Date;

public class BatchSample {
    private static void tc1(){
        Connection conn = null;
        PreparedStatement pstmt = null;
        int num=0;
        try {
            long startTime = new Date().getTime();
            conn = DbUtils.getConnection();
            conn.setAutoCommit(false);
            String sql = "insert into employee(eno,ename,salary,dname) values(?,?,?,?)";
            for (int i = 100000;i < 200000;i ++){
                pstmt = conn.prepareStatement(sql);
                pstmt.setInt(1,i);
                pstmt.setString(2,"员工"+i);
                pstmt.setFloat(3,4000f);
                pstmt.setString(4,"市场部");
                num = pstmt.executeUpdate()+num;
            }
            if (num != 0){
                System.out.println("成功"+num);
            }else {
                System.out.println("失败"+num);
            }
            conn.commit();
            long endTime = new Date().getTime();
            System.out.println(endTime-startTime);
        } catch (Exception e) {
            e.printStackTrace();
            try {
                if (conn != null && !conn.isClosed()){
                    conn.rollback();
                }
            } catch (SQLException ex) {
                e.printStackTrace();
            }
        }finally {
            DbUtils.closeConnection(null,pstmt,conn);
        }
    }

    private static void tc2(){
        Connection conn = null;
        PreparedStatement pstmt = null;
        int num=0;
        try {
            long startTime = new Date().getTime();
            conn = DbUtils.getConnection();
            conn.setAutoCommit(false);
            String sql = "insert into employee(eno,ename,salary,dname) values(?,?,?,?)";
            for (int i = 200000;i < 300000;i ++){
                pstmt = conn.prepareStatement(sql);
                pstmt.setInt(1,i);
                pstmt.setString(2,"员工"+i);
                pstmt.setFloat(3,4000f);
                pstmt.setString(4,"市场部");
                num = pstmt.executeUpdate()+num;
                pstmt.addBatch();
            }
            if (num != 0){
                System.out.println("成功"+num);
            }else {
                System.out.println("失败"+num);
            }
            pstmt.executeBatch();
            conn.commit();
            long endTime = new Date().getTime();
            System.out.println(endTime-startTime);
        } catch (Exception e) {
            e.printStackTrace();
            try {
                if (conn != null && !conn.isClosed()){
                    conn.rollback();
                }
            } catch (SQLException ex) {
                e.printStackTrace();
            }
        }finally {
            DbUtils.closeConnection(null,pstmt,conn);
        }
    }

    public static void main(String[] args) {
        tc1();
        tc2();
    }
}