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...
`update_time` datetimeDEFAULTNULL,PRIMARYKEY (`id`) ) ENGINE=InnoDBDEFAULTCHARSET=utf8;-- --- Records of actor-- ---BEGIN;INSERTINTO`actor` (`id`, `name`, `update_time`)VALUES(1,'a','2017-12-02 15:27:18');INSERTINTO`actor` (`id`, `name`, `update_time`)VALUES(2,'b','2...
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...
详见 “Optimizing INFORMATION_SCHEMA Queries”[7] 21 Select tables optimized away 优化器确定:①最多返回1行;②要产生该行的数据,要读取一组确定的行,时会出现此提示。一般在用某些聚合函数访问存在索引的某个字段时,优化器会通过索引直接一次定位到所需要的数据行完成整个查询时展示,例如下面这条SQL。 代码语...
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...
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...
Is your feature request related to a problem? Please describe. DBeaver option "Explain Execution Plan" is greyed out in SQL Server connections Describe the solution you'd like Implement option "Explain Execution Plan" by parsing output f...
•Slow_queries:慢查询的次数。 •Innodb_rows_read:Select查询返回的行数 •Innodb_rows_inserted:执行INSERT操作插入的行数 •Innodb_rows_updated:执行UPDATE操作更新的行数 ...
--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’queryexecutionplan’.这个和Oracle的执行计划是一个感念。 YourgoalsaretorecognizetheaspectsoftheEXPLAINplanthatindicateaqueryisoptimizedwell,andtolearntheSQLsyntaxandindexingtechniquestoimprovetheplanifyouseesomeinef...