Step04是执行step03结果集和T4表left join的步骤 根据缩进格式,首先执行stop03结果集<03>和T4表的left join,然后执行where条件过滤,最后执行GROUP BY T4表是视图,所以GBase转为子查询SubQuery6,基表clm_XXXX为单表没有单表条件,因此OPERATION为Table 这一步的结果集<03>的分布列本身为maXXXX(由step03中的MOTION...
#接着假定要取出userid为1的最近3次的购买记录,用的就是联合索引userid_2了,因为在这个索引中,在userid=1的情况下,buy_date都已经排序好了 mysql>explainselect*frombuy_logwhereuserid=1orderbybuy_datedesclimit3;+--+---+---+---+---+---+---+---+---+---+|id|select_type|table|type|...
For most queries the total cost is what matters, but in contexts such as a subquery in EXISTS, the planner will choose the smallest start-up cost instead of the smallest total cost (since the executor will stop after getting one row, anyway). Also, if you limit the number of rows to ...
I Cant Explain It, But I'll Try Go Big or Don’t Get Home Roes of Stuff Is this Utopia? Saturation Point Singapore Delivers On to the Next Rocky Road This Isn’t a Movie I Am a Sucker for a Deal Costa Christina I Said I Was Going...
EXPLAIN SELECT * FROM s1 ORDER BY common_field LIMIT 10; 9. Using temporary 在许多查询的执行过程中,MySQL可能会借助临时表来完成一些功能,比如去重、排序之类的,比如我们在执行许多包含`DISTINCT '、GROUP BY'、‘UNION`等子句的查询过程中,如果不能有效利用索引来完成查询,MysQL很有可能寻求通过建立内部的临...
A STOP bu no START predicate is present ! A SARG predicate is present (additionally, !). A heuristic to indicate Top-N clauses: if the number of rows drops for TBSCAN or IXSCAN but there are no predicates, it must be a Top-N limit. This logic is incomplete, of course....
aultrasonic load warning, the machine will automatically stop when warning. safety limit switch opening the door. 当警告时,超音波装载警告,机器将自动地停止。 安全打开门的限位开关。[translate] aSomeday, you will find the one, who will watch every sunrise with you until the sunset of your lif...
I thought I am not unnecessary to stand completely highly and measure in you limit and guide own consciousness and the behavior, the testimony my growth is diligently I should do. [translate] a字典是我们学英语的一种好工具 The dictionary is we studies English one kind of good tool [translate...
在日常的MYSQL优化中我们常常看到这样一个关键词:explain,例如这种: EXPLAIN SELECT * FROM Cloud_Order WHERE money > 10; explain是什么呢?使用 EXPLAIN 关键字可以模拟优化器执行SQL查询语句,从而知道MySQL是如何处理你的SQL语句的。这可以帮你分析你的查询语...猜...
When the cube is scrambled, it might seem to the untrained eye that the cubies can turn any old way. Yet, that's not the case. Because of the way the mechanism works, there are certain principles that limit the cubies' positions. For instance, no matter how you turn the cube, you ...