KEY `idx_name` (`name`) ) ENGINE=InnoDB AUTO_INCREMENT=4DEFAULTCHARSET=utf8;-- --- Records of film-- ---BEGIN;INSERTINTO`film` (`id`, `name`)VALUES(2,'film 2');INSERTINTO`film` (`id`, `name`)VALUES(3,'film0');INSERTINTO`film` (`id`, `name`)VALUES(1,'film1');COMMIT...
MySQL explains how it would process the statement, including information about how tables are joined and in which order. For information about using EXPLAIN to obtain execution plan information, see Section 8.8.2, “EXPLAIN Output Format”. 当...
MySQL 的执行计划是数据库查询优化的重要工具,帮助开发者理解 SQL 查询的执行过程,从而进行性能调优。执行计划详细展示了 MySQL 如何解析、优化和执行 SQL 语句,直接影响查询的效率和性能。1. 执行计划的基本概念执行计划是 MySQL 对 SQL 查询进行分析后生成的一组指令,描述了如何从表中获取数据。执行计划包括了所使...
unionM,N: The row refers to the union of the rows with id values of M and N. derivedN: The row refers to the derived table result for the row with an id value of N. A derived table may result, for example, from a subquery in the FROM clause. subqueryN: The row refers to the...
explain可用来分析SQL的执行计划。格式如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 {EXPLAIN|DESCRIBE|DESC}tbl_name[col_name|wild]{EXPLAIN|DESCRIBE|DESC}[explain_type]{explainable_stmt|FORCONNECTIONconnection_id}{EXPLAIN|DESCRIBE|DESC}ANALYZEselect_statementexplain_type:{FORMAT=format_name}fo...
Query Plan Fragment 0 [SINGLE] Output layout: [c_custkey, o_orderkey, o_orderstatus] Output partitioning: SINGLE [] Stage Execution Strategy: UNGROUPED_EXECUTION - Output[c_custkey, o_orderkey, o_orderstatus] => [[c_custkey, o_orderkey, o_orderstatus]] - RemoteSource[1] => [[c...
EXPLAIN is used to obtain a query execution plan (that is, an explanation of how MySQL would execute a query). 简单翻译一下,就是explain用于获取查询执行计划(即MySQL是如何执行一个查询的)。 工作中,我们会遇到慢查询,这个时候我们就可以在select语句之前增加explain关键字,模拟MySQL优化器执行SQL语句,从而...
--优化器根据表,列,索引以及查询条件,指定了一个查询路径,以实现高效的性能,这个查询的路径就称为’query execution plan’. 这个和Oracle的执行计划是一个感念。 Your goals areto recognize the aspects of the EXPLAIN plan that indicate a query is optimizedwell, and to learn the SQL syntax and indexing...
关于这些性能指标的解读,可以参照 pg_proctab: Accessing System Stats in PostgreSQL,无疑,有了 DSEF,可以大大方便我们对比分析不同的访问路径,而不仅仅只是从一个 Execution time 来对比,给作者打 call! 小结 赶紧用起来吧!SQL 性能诊断利器+1。下一期与各位分享等待事件的诊断利器。 参考 github.com/ardentperf...
EXPLAIN is used to obtain a query execution plan (that is, an explanation of how MySQL would execute a query). 简单翻译一下,就是explain用于获取查询执行计划(即MySQL是如何执行一个查询的)。 工作中,我们会遇到慢查询,这个时候我们就可以在select语句之前增加explain关键字,模拟MySQL优化器执行SQL语句,从而...