EXPLAIN :模拟Mysql优化器是如何执行SQL查询语句的,从而知道Mysql是如何处理你的SQL语句的。分析你的查询语句或是表结构的性能瓶颈。 (一)ID (二)select_type列:数据读取操作的操作类型 1、SIMPLE:简单的select 查询,SQL中不包含子查询或者UNION。 2、PRIMARY:查询中包含复杂的子查询部分,最外层查询被标记为PRIMARY...
mysql使用 explain来查看执行计划:根据MySQL执行计划的输出,分析索引使用情况、扫描的行数可以预估查询效率;进而可以重构SQL语句、调整索引,提升查询效率。 https://www.cnblogs.com/sunjingwu/p/10755823.html 一.id ,select 查询*** 1 id相同,从上往下一次执行;2 id不同,id越大优先级越高,越先被执行。 ......
ClickHouse是俄罗斯的Yandex于2016年开源的列式存储数据库(DBMS),使用C++语言编写,主要用于在线分析处理查询(OLAP),能够使用SQL查询实时生成分析数据报告。 OLAP(On-Line Analytical Processing)翻译为联机分析处理,专注于分析处理,从对数据库操作来看,OLAP是对数据的查询; OLTP(on-line transaction processing)翻译为联机...
The EXPLAIN command will fail if you use it for other SQL commands, such as data definition language (DDL) or database operations. The EXPLAIN output relative unit costs are used by Amazon Redshift to choose a query plan. Amazon Redshift compares the sizes of various resource estimates to ...
The number of rows that are affected by a data manipulation language (DML) statement. This metric is displayed only when a DML statement is executed. Dag instance count The number of DAG instances in the execution plan. A large value indicates a complex query with a high DOP. Fragment ...
The TREE format, while compact and easy to read and understand for a human reader, would require manual parsing to analyze in code. With EXPLAIN FORMAT=JSON you can get a JSON object instead, which can be handled with JSON functions either client-side in your preferred programming language, ...
Raised when a request attempts to initiate an operation that is not supported. HTTP Status Code: 400 For more information about using this API in one of the language-specific AWS SDKs, see the following: 이 페이지에서 페이지 내용이 도움이 되었습니까?
Default: 0. graph— Prints a graph described in the DOT graph description language. Default: 0. compact— Prints graph in compact mode if graph setting is enabled. Default: 1. Example: EXPLAIN PIPELINE SELECT sum(number) FROM numbers_mt(100000) GROUP BY number % 4;...
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In 2017, researchers at Google introduced the transformer architecture, which has been used to develop large language models, like those that power ChatGPT. In natural language processing, a transformer encodes each word in a corpus of text as a token and then generates an attention map, which...