在提出这个问题之前,我应该说,我对数据库的效率知之甚少,不久后数据库的效率就会变得显而易见。
这是一个相当简单的问题:
I d like to store attendance to events within a mysql database. I ve thought of two possible methods (there are more, I m sure):
attendance row in the events table, containing a comma separated list of user idsattendance table, containing two columns, event_id and user_id 我的直觉说,方法2是最有效率的-- 虽然多行必须返回和穿行,但这可能比在刻录的字符串中搜索特定的user_id 的成本要低...
有人能证实吗?
第二个选项更好。 在逗号分隔字符串中搜索需要时间 。
但在第二个选项中,确保 event_id 和 user_id 为 AFOREIGN KEYS 。
这将为列提供 INDEX ,您将获得更好的搜索结果。
创建新桌子!
否则您将无法利用 MySQL 的关联方面, 您所运行的每个查询将不得不分析 csv 条目的结果( 极低效率)
I noticed that there were some threads with similar questions, and I did look through them but did not really get a convincing answer. Here s my question: The subquery below returns a Table with 3 ...
<?php $con=mysql_connect("localhost","mts","mts"); if(!con) { die( unable to connect . mysql_error()); } mysql_select_db("mts",$con); /* date_default_timezone_set ("Asia/Calcutta"); $date = ...
我把我的用心从使用QQL转向MySQL。 它与凯科特合作,现在不工作,因为我已经改变,使用MySQL。 这里的错误信息是:
We have a restaurant table that has lat-long data for each row. We need to write a query that performs a search to find all restaurants within the provided radius e.g. 1 mile, 5 miles etc. We have ...
Is it possible in php to return a specific row of data from a mysql query? None of the fetch statements that I ve found return a 2 dimensional array to access specific rows. I want to be able to ...
Our website was developed with a meta tag set to... <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> This works fine for M-dashes and special quotes, etc. However, I ...
What are some of the strategies being used for pagination of data sets that involve complex queries? count(*) takes ~1.5 sec so we don t want to hit the DB for every page view. Currently there are ~...
My table looks like person_id | car_id | miles ------------------------------ 1 | 1 | 100 1 | 2 | 200 2 | 3 | 1000 2 | 4 | 500 I need to ...