EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joins using a nested-loop join method. Thismeans that MySQL reads a row from the first ...
DELIMITER //CREATEPROCEDUREinsert_s1 (INmin_numINT(10),INmax_numINT(10))BEGINDECLAREiINTDEFAULT0;SETautocommit =0;REPEATSETi = i +1;INSERTINTOs1VALUES((min_num + i),rand_string(6),(min_num +30* i +5),rand_string(6),rand_string(10),rand_string(5),rand_string(10),rand_string(...
https://dev.mysql.com/doc/workbench/en/wb-performance-explain.html 标准框--红色:全表扫描(花费极高),全索引扫描(花费高) 圆脚框--group/sort,分组或排序 钻石框--joins Framed boxes(有外框)--子查询。 Join type连接类型: https://dev.mysql.com/doc/refman/8.0/en/explain-output.html#explain-joi...
{ "transformations_to_nested_joins": { "transformations": [ "parenthesis_removal" ] /* transformations */, "expanded_query": "/* select#2 */ select group_concat(`f`.`title` order by `f`.`title` ASC separator ', ') from `film` `f` join `film_category` `fc` join `film_actor`...
EXPLAIN作为MySQL的性能分析神器,读懂其结果是很有必要的,然而我在各种搜索引擎上竟然找不到特别完整的解读。都是只有重点,没有细节(例如type的取值不全、Extra缺乏完整的介绍等)。 所以,我肝了将近一个星期,整理了一下。这应该是全网最全面、最细致的EXPLAIN解读文章了,下面是全文。
You can also use EXPLAIN to check whether the optimizer joins the tables in an optimal order. To give a hint to the optimizer to use a join order corresponding to the order in which the tables are named in a SELECT statement, begin the statement with SELECT STRAIGHT_JOIN rather than just...
EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joins using a nested-loop join method. Thismeans that MySQL reads a row from the first...
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EXPLAIN语句返回MYSLQ的执行计划,通过他返回的信息,我们能了解到MYSQL优化器是如何执行SQL语句的,通过分析他能帮助你提供优化的思路。 语法 MYSQL 5.6.3以前只能EXPLAIN SELECT; MYSQL5.6.3以后就可以EXPLAIN SELECT,UPDATE,DELETE EXPLAIN 语法例子: mysql> explain select customer_id,a.store_id,first_name,last_na...
If you want to find more information about understanding EXPLAIN output, MySQL manual EXPLAIN page is good place to start. Related Feedback Wanted: Making EXPLAIN Require Less Privileges for INSERT/UPDATE/DELETE StatementsFebruary 20, 2023In "MySQL" Many-table joins in MySQL 5.6March 6, 2014In ...