7、unique_subquery表示唯一子查询。例如有如下语句执行时: value in(select primary_key from single_table where ...) 对于in子句来说,当in子句里的子查询返回的是某一个表的主键时,type显示为unique subquery。 8、index_subquery当有如下语句执行时: value in(select key_column from single_table where .....
AI代码解释 mysql>explain select*from employees where first_name='Mayuri'and last_name>'Alpay'\G***1.row***id:1select_type:SIMPLEtable:employeespartitions:NULLtype:rangepossible_keys:idx_akey:idx_akey_len:124ref:NULLrows:226filtered:100.00Extra:Using index condition 虽然这里显示了 “Using index...
org.fcitx.Fcitx5.Addon.TableExtra.metainfo.xml.in bump version Repository files navigation README Requirements: You need to install fcitx5-chinese-addons and libime first. ``` mkdir build cd build cmake .. -DCMAKE_INSTALL_PREFIX=<fcitx's prefix> cmake --build . cmake --install . ...
CREATE TABLE `example_table` (`id` int(11) NOT NULL AUTO_INCREMENT,`name` varchar(255) NOT NULL,PRIMARY KEY (`id`) USING BTREE,UNIQUE KEY `unique_name` (`name`) USING BTREE,`created_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,`updated_at` timestamp NOT NULL DEFAULT ...
I have recently experienced every time I create a new database in Access I see 5 new tables that are supposed to be hidden, I can open them, but I cannot...
value in(select key_column from single_table where ...) 与上面的相似,表示对于in子句来说,当in子句里的子查询返回的是某一个表的二级索引列(非主键列)时,type显示为index_subquery。 9、range: 在有索引的列上取一部分数据。常见于在索引列上执行between and操作。
After picking one, here is the final result for the Excel Table Style!If you like this Excel tip, please share itJohn Michaloudis Founder & Chief Inspirational Officer at MyExcelOnline.com John Michaloudis is a former accountant and finance analyst at General Electric, a Microsoft MVP ...
Extra为Using temporary说明,需要建立临时表(temporary table)来暂存中间结果。 这类SQL语句性能较低,往往也需要进行优化。 典型的,group by和order by同时存在,且作用于不同的字段时,就会建立临时表,以便计算出最终的结果集。 六、【Using join buffer (Block Nested Loop)】 ...
table: employees partitions: NULL type: range possible_keys: idx_a key: idx_a key_len: 127 ref: NULL rows: 1 filtered: 100.00 Extra: Using where; Using index Using index condition 查询数据时如果使用 index condition down索引条件下推就会在执行计划的 extra 字段中出现 "Using index condition"。