循环分批从数据库获取数据

Posted 2022-12-08 爱锅巴

模拟根据查询出的总数循环分批从数据库获取数据

很多时候我们并不能在jvm存住一个多达一两万元素的List，如果单个元素过大不加以控制，有可能会造成内存溢出，所以需要分批查询数据

public static void main(String[] args) 
    //事先查出的总数
    int totalNum = 13031;
    //每次拿取数量
    int preNum = 1000;
    //循环过的数量
    int passNum = 0;
    do 
        System.out.println("select * from a limit " + passNum + "," + preNum);
        passNum += preNum;
     while (passNum < totalNum);

打印结果，每次只拿取1000条数据，保证程序中不会出现太大的数组导致内存溢出

select * from a limit 0,1000;
select * from a limit 1000,1000;
select * from a limit 2000,1000;
select * from a limit 3000,1000;
select * from a limit 4000,1000;
select * from a limit 5000,1000;
select * from a limit 6000,1000;
select * from a limit 7000,1000;
select * from a limit 8000,1000;
select * from a limit 9000,1000;
select * from a limit 10000,1000;
select * from a limit 11000,1000;
select * from a limit 12000,1000;
select * from a limit 13000,1000;