MySQL优化:定位慢查询的两种方法以及使用explain分析SQL:https://baijiahao.baidu.com/s?id=1644795692359019265&wfr=spider&for=pc [4] 优化Sequences:https://www.docs4dev.com/docs/zh/mysql/5.7/reference/order-by-optimization.html [5
这就提到了MySQL的分析语句Explain,以下是我在工作中遇到的一个总是超时的SQL,我对这个SQL的Explain,我们先掌握一下Explain的返回的信息的学习,否则你看都看不懂,怎么通过explain返回的信息去定位问题呢. (后面我还会用这个SQL来做分析,稍微优化一下,让他从两三秒钟返回结果变成零点零几秒) 一 例子 EXPLAIN SELECT...
SQL 语句 通用语法 通用表表达式 ALTER DATABASE ALTER OUTLINE ALTER SEQUENCE MERGE ALTER TABLE ALTER TABLEGROUP ALTER USER ALTER VIEW ANALYZE CREATE DATABASE CREATE INDEX CREATE OUTLINE DROP RESTORE POINT CREATE SEQUENCE CREATE TABLE CREATE TABLEGROUP CREATE USER CREATE VIEW DEALLOCATE PREPARE DELETE DESC...
CREATE SEQUENCE ORDERSEQ START WITH 1 INCREMENT BY 1 NOMAXVALUE NOCYCLE CACHE 24 例如: create sequence pk_only_empid; select NEXTVAL FOR pk_only_empid from (values 1) as tmp; 1. 2. 3. 4. 5. 6. 如何关闭表的日志 ALTER TABLE TABLE_NAME ACTIVE NOT LOGGED INIALLY 1. 如何获取SQL执行计...
Understand Complex SQL Queries Easily using AI Expert SQL Query Write down your SQL Query in the following box and select target datbase. Once done, click onExplain CodeButton to generate the explanation of your SQL query. SELECT U.userid, U.fullname, U.emailid, U.state, U.country, U....
参考: 优化Sequences Orderby 排序优化 理解mysql的临时表和文件排序 【IT老齐338】MySQL Extra常见信息解析 【大厂文章速读】字节跳动-慢SQL分析与优化(extra出现这几项,一定要加倍注意)
Hive SQL在执行之前会将SQL转换为MapReduce任务,因此需要了解具体的转换过程。可以通过explain关键字来查看具体的执行计划。通过执行计划能看到 SQL 程序转换成相应计算引擎的执行逻辑,从而能够实现更有针对性的优化(比如有些看似等价的SQL写法实则不等价)。
The execution plan for a specific Amazon Redshift query statement breaks down execution and calculation of a query into a discrete sequence of steps and table operations that eventually produce a final result set for the query. For information about query planning, seeQuery processing. ...
(6)FIRST ROW:获取查询的第一条记录。 (7)SEQUENCE:使用了Oracle序列。 (8)LOAD AS SELECT:使用SELECT进行直接路径的INSERT操作。 (9)FIXED TABLE:访问固定的(X$/V$)表。 (10)FIXED INDEX:访问固定的索引。 (11)WINDOW BUFFER:支持分析函数的内部操作。
The sequence in which the SELECT is processed is described by the order of the rows in the result table. Structure of the EXPLAIN Result Table Column Description Data Type SCHEMANAME Schema name/owner CHAR(64) TABLENAME Table Name CHAR(64) COLUMN_OR_INDEX Shows which key column, ...