The 'do-while' loop can be implemented (in C) as: inti=5; do { printf("%d",i); i--; }while(i>=0); where 'i' is the loop variable. Answer and Explanation:1 Both for loop and while loop can run multiple statements
2、执行查询explain select * from a join b on a_id=b_id where b_id in (select c_id from c); mysql> explain select * from a join b on a_id=b_id where b_id in (select c_id from c); EXPLAINSELECT*FROMaJOINbONa_id=b_idWHEREb_idIN(SELECTc_idFROMc); id select_typetablepa...
类似于两表连接中被驱动表的eq_ref访问方法,unique_subquery是针对在一些包含IN子查询的查询语句中,如果查询优化器决定将IN子查询转换为EXISTS子查询,而且子查询可以使用到主键进行等值匹配的话,那么该子查询执行计划的type列的值就是unique_subquery,比如下面的这个查询语句: mysql> EXPLAIN SELECT * FROM s1 WHERE ...
If you want to make your queries as fast as possible, look out for Extra column values of Using filesort and Using temporary, or, in JSON-formatted EXPLAINoutput, for using_filesort and using_temporary_table properties equal to true. 大概的意思就是说,如果你想要优化你的查询,那就要注意extra...
UNCACHEABLE SUBQUERY A subquery for which the result cannot be cached and must be re-evaluated for each row of the outer query UNCACHEABLE UNION The second or later select in a UNION that belongs to an uncacheable subquery (see UNCACHEABLE SUBQUERY) SIMPLE 查询语句中不包含UNION或者子查询的...
I did't know that "i" was already defined since my professor usually uses it in examples not pertaining to imaginary numbers. I also took your advice on the file name. Oh, I'm making a loop for forwards euler, since our professor doesn't want us to use ode...
How to explain the code below in the loop so I... Learn more about for loop, csv, faq, process a sequence of files
EXPLAINSELECT*FROMsc_tableWHEREkey_1IN(SELECTkey_1FROMsc_table_1); 如上,查询语句中有一个子查询,但执行计划中两个表的id都是1,说明查询优化器将子查询转换成连接查询。 二、 带UNION子句的查询,每个SELECT关键字同样会对应一个id,但是还有一点不通的特征,如下: ...
Range checked for each Record(index map: N) 没有找到理想的索引,因此对于从前面表中来的每一个行组合,MYSQL检查使用哪个索引,并用它来从表中返回行。这是使用索引的最慢的连接之一 FirstMatch(tbl_name) 5.6.x开始引入的优化子查询的新特性之一,常见于where字句含有in()类型的子查询。如果内表的数据量比较...
(APITest.test_cache_miss_explanations_new_function_in_loop) because: never seen function: <lambda> id=5036820896 defined at /Users/necula/Source/jax/tests/api_test.py:4549 but seen another function defined on the same line; maybe the function is being re-defined repeatedly, preventing caching...