土人设计----再造城市滨水景观 图文.doc

土人设计----再造城市滨水景观_图文从MysqlEXPLAIN探寻数据库查询优化作者:蘑菇 日期:2010-07-2016:37:20 阅读:?load=read&id=|SELECTselect_optionsEXPLAINtbl_name和DESCRIBEtbl_name的作用是一样的,用于显示表结构等信息。当我们在select语句前加上EXPLAIN后,Mysql将告诉我们它是如何处理select语句的,提供表之间的联结方式、使用索引等有关信息。,我用了joomla的文章表做测试,因为要演示优化过程,所以我事先删除了表里除主键之外的所有索引。这里用到了三个表:mysql>explainjos_content;+------------------+------------------+------+-----+---------------------+----------------+|Field      |Type       |Null|Key|Default       |Extra     |+------------------+------------------+------+-----+---------------------+----------------+|id        |int(11unsigned|NO  |PRI|NULL        |auto_increment||title      |varchar(255   |NO  |   |           |        ||alias      |varchar(255   |NO  |   |           |        ||title_alias   |varchar(255   |NO  |   |           |        ||introtext    |mediumtext    |NO  |   |NULL        |        ||fulltext     |mediumtext    |NO  |   |NULL        |        ||state      |tinyint(3    |NO  |   |0          |        ||sectionid    |int(11unsigned|NO  |   |0          |        ||mask       |int(11unsigned|NO  |   |0          |        ||catid      |int(11unsigned|NO  |   |0          |        ||created     |datetime     |NO  |   |0000-00-0000:00:00|        ||created_by    |int(11unsigned|NO  |   |0          |        ||created_by_alias|varchar(255   |NO  |   |           |        ||modified     |datetime     |NO  |   |0000-00-0000:00:00|        ||modified_by   |int(11unsigned|NO  |   |0          |        ||checked_out   |int(11unsigned|NO  |   |0          |        ||checked_out_time|datetime     |NO  |   |0000-00-0000:00:00|        ||publish_up    |datetime     |NO  |   |0000-00-0000:00:00|        ||publish_down   |datetime     |NO  |   |0000-00-0000:00:00|        ||images      |text       |NO  |   |NULL        |        ||urls       |text       |NO  |   |NULL        |        ||attribs     |text       |NO  |   |NULL        |        ||version     |int(11unsigned|NO  |   |1          |        ||pa