DROP database IF EXISTS `explain_test`; create database `explain_test` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci; -- switch database use `explain_test`; -- --- -- table structure for `tb_book` -- --- DROP TABLE IF EXISTS `tb_book`; CREATE TABLE `tb_...
The output is displayed in a tree structure and contains detailed execution information of each operator at each phase. The output of the EXPLAIN ANALYZE statement contains the following parts: query plan, advice, cost, and resource. Query Plan The query plan part provides detailed execution ...
Structure Query Language(结构化查询语言)简称SQL,它被美国国家标准局(ANSI)确定为关系型数据库语言的美国标准,后被国际化标准组织(ISO)采纳为关系数据库语言的国际标准。数据库管理系统可以通过SQL管理数据库;定义和操作数据,维护数据的完整性和安全性 3.2 SQL的分类 DQL:数据查询语言(凡是带有select关键字的都是查询...
这些工作甚至有些地方会有专人来做,就叫 database optimization。 其实数据库优化很大一部分就是要读懂 planning,MySQL 的 optimization 在其文档里面有专门的一章,关于如何读懂 explain 的结果有专门的一节。我们这里着重看 explain 那块,顺便了解一些其他的优化。 表格的 structure 是否合理 合适的 index 是否已經到...
Source Database : testExplain Target Server Version : 50550 File Encoding : utf-8 Date: 08/05/2016 18:06:12 PM */ SETNAMES utf8; SETFOREIGN_KEY_CHECKS=0; --- --Table structure foruser --- DROPTABLEIFEXISTS<span style="color
DROP database IF EXISTS `explain_test`; create database `explain_test` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci; -- switch database use `explain_test`; -- --- -- table structurefor`tb_book` -- --- DROP TABLE IF EXISTS `tb_...
Structure Syntax <explain_statement> ::= EXPLAIN [(<result_table_name>)] <query_statement> | EXPLAIN [(<result_table_name>)] <single_select_statement> Examples Database Administration, EXPLAIN Statement Explanation The EXPLAIN statement can be used to check the effect that creating or deleting ...
Source Database : explain-learn Target Server Type : MYSQL Target Server Version : 50624 File Encoding : 65001 Date: 2021-03-05 17:30:25 */ SET FOREIGN_KEY_CHECKS=0; -- --- -- Table structure for tb_subject -- --- DROP TABLE IF EXISTS `tb_...
The query and database structure The following is the structure of the two tables used by this example query (postsandvotes): 1 2 3 4 5 6 7 8 9 10 11 12 CREATETABLE`posts` ( `Id`int(11)NOTNULL, `AcceptedAnswerId`int(11)DEFAULTNULL, ...
The structure of the return value XML looks like this:XML Kopiera \<?xml version="1.0" encoding="utf-8"?> <dsql_query> <sql>. . .</sql> <params /> <dsql_operations> <dsql_operation> . . . </dsql_operation> [ . . . n ] <dsql_operations> </dsql_query> ...