{ "table_name": "t1", "access_type": "ALL", "rows_examined_per_scan": 1, "rows_produced_per_join": 1, "filtered": "100.00", "cost_info": { "read_cost": "0.25", "eval_cost": "0.10", "prefix_cost": "0.35", "data_read_per_join": "56" }, "used_columns": [ "id"...
explain执行计划包含的信息 其中最重要的字段为:id、type、key、rows、Extra 各字段详解 id select查询的***,包含一组数字,表示查询中执行select子句或操作表的顺序 三种情况: 1、id相同: 执行顺序由上至下 2、id 不同:如果是子查询,id的序号会递增,id值越大优先级越高,越先被执行 3、id相同又不同(两种...
explain的作用: 判断mysql语句执行的时间效率分析;1、在navicate客户端使用sql语句的时候,整体图形如下2、名词解释 一、select_type数据列指明各“单位...在一起。MariaDB中,不会在默认优化器模式下先处理IN(subquery)查询内部的子查询,而是读取外部的employees数据表,再执行子查询时,dependent关键字就会出现在select_...
mysql>explainSELECTid,titleFROMseo_php_articlewhereis_delete=0orderbyidasclimit66500,500;+---+---+---+---+---+---+---+---+---+---+|id|select_type|table|type|possible_keys|key|key_len|ref|rows|Extra|+---+---+---+---+---+---...
id) FROM big_data_user bdu2 GROUP BY bdu2.phone HAVING count(*)> 1) b); EXPLIAN 出来的信息有 12 列,分别是 id、select_type、table、partitions、type、possible_keys、key、key_len、ref、rows、filtered、Extra id - 查询标识 查询标识,表示 SQL 语句中执行 SELECT 子句或者是操作的顺序。
The request accepts the following data in JSON format. gremlin The Gremlin explain query string. Type: String Required: Yes HTTP/1.1 200output If the action is successful, the service sends back an HTTP 200 response. The response returns the following as the HTTP body. ...
比较全的Show命令的使用可参考: http://blog.phpbean.com/a.cn/18/ 慢查询日志 慢查询日志开启: 在配置文件my.cnf或my.ini中在[mysqld]一行下面加入两个配置参数 log-slow-queries=/data/mysqldata/slow-query.log long_query_time=2 注:log-slow-queries参数为慢查询日志存放的位置,一般这个目录要有mysql...
database in ('datasets','system') group by database,table order by database,cnt desc limit 2 by database; 打开全部的参数的执行计划 EXPLAIN header=1, actions=1,description=1 SELECT number from system.numbers limit 10; 2)AST 语法树 EXPLAIN AST SELECT number from system.numbers limit 10...
New in version 1.13. readPreference MongoDB\Driver\ReadPreference Read preferenceto use for the operation. Defaults to the collection's read preference. typeMap array Thetype mapto apply to cursors, which determines how BSON documents are converted to PHP values. Defaults to the collection's type...
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