iptables limit 能否对每ip进行? iptables -A INPUT -s 10.1.1.1/24 -p udp -m limit --limit 1/sec -j ACCEPT 这样会将整个c总共的limit 设成1/sec 能否对每ip设limit? 总不能写250行吧,呵呵 请教了
1. select * from tablename limit 100,15 从100条记录后开始取15条 (实际取取的是第101-115条数据) 2. select * from tablename limit 100,-1 从第100条后开始-最后一条的 本文来自ChinaUnix博客,如果查看原文请点:http://blog.chinaunix.net/u/29375/showart_1892407.html
在我们使用查询语句的时候,经常要返回前几条或者中间某几行数据,这个时候怎么办呢?不用担心, mysql 已经为我们提供了这样一个功能。 SELECT * FROM table limit [offset,] rows | rows OFFSET offset limit 子句可以被用于强制 SELECT 语句返回指定的记录数。limit 接受一个或两个数字参数。参数必须是一个整数常量。如果给定两个参数,第一个参数指定第一个返回记录行的偏移量,第二个参数指定返回记录行的最大数目。初始记...
if your programe execute a high-cost-operation under multi-thread and want to assign the number that the high-cost-operation can be invoked at the same time... actually "Thread.sleep()" can't do this, because that your programe is running under multi-thread environment so check the following simple code, hope it is helpful :) [code] public class ConcurrentControler { private int limit...
select * from table limit 5,10; #返回第6-15行数据 select * from table limit 5; #返回前5行 select * from table limit 0,5; #返回前5行 字串5 字串5 性能优化: 字串7 字串8 基于MySQL5.0中limit的高性能,我对数据分页也重新有了新的认识. 1. Select * From cyclopedia Where ID>=( Select Max(ID) From ( Select ID From cyclopedia Order By ID limit 90001 ) As tmp ) limit 100; 2. Select * From cyclopedia ...
In this third case we get to see some really fun stuff: The effect of ANALYZE on index selection for a three table join, an ORDER BY with limit optimization, and documented evidence that what we'll fix makes a night and day difference for the better. The customer in this case runs a gaming website using the Neocrome Land Down Under website engine. The customer's website averages...
看mysql手册,某些时候limit也能起到优化作用,但只是简单几句话,不理解啊。 有个表,有ID,keyword等字段,在ID上有唯一关键字索引。keyword是逗号分隔的字符串(非SET)。 如执行 select * from table where find_in_set("xxx",keyword ) order by id DESC limit 10 find_in_set好像有索引也用不上,那么会不会遍历整个表呢? 还是先排好序,然后查询出10记录就返回了? [ 本帖最后由 只爱一点点 于 2007-2-27 21:49 编辑 ]