b-tree structure if the name field is an index, then if there are seven pieces of data in the table, all nodes in the b-tree also have seven pieces of data, so isn t scanning the entire data area as efficient as scanning the entire index area? ...
reference article: Innodb lock mechanism: Next-Key Lock talk about-jyzhou-blog Park Why should Next-Key Lock be designed as a left open and right closed interval? Can t be designed as a gap lock? Why is right closed? ask the boss to answer. < ...
The question originates from this article: MySQL answering questions using filesort VS using temporary in the article: mysql> explain select * from t1 force index(id), t2 where t1.id=1 and t1.col1 = t2.col2 order by t2.col1 ; +----+-------------...
< H1 > as shown in the title: < H1 > EXPLAIN execution Plan: the following is my table structure. It takes 7 seconds to query more than 10, 000 pieces of data. CREATE TABLE order_copy ( id bigint (20) NOT NULL AUTO_INCREMENT, seq_id bigint...
tinyint that has been used before for fields that represent data types or states has not paid attention to the bit type. After consulting the data, we know that bit is stored in binary format: bounded 0 or bounded 1 its storage unit is direc...
I have a table service_message that contains about 600000 pieces of data, which records when different devices receive messages: SHOW CREATE TABLE service_message CREATE TABLE `service_message` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `device_id` I...
there is a usr table containing uid,username business table 1, the information stored are fields uid,username business table 2, and only uid, (multiple data in business table 2 corresponds to one data in business table 1) the environmental backgrou...
background and phenomena the amount of data in the report_product_sales_ data table is 28 million; it has been tested that when the, order by primary key id,limit reaches 49 under the current data volume, the PRIMARY primary key index can be used w...
< hr > This internal server error error occurs when < H2 > climbs to a range of $I between 35 and 45. < H2 > < hr > class Pacong extends Base { public function test(){ header("content-type:text html;charset=utf-8"); set_time_limi...
the data I passed into the table component data is tableDatasTotal: [] { NickName: 1 , ID: 123123 , yyDayScore: -1223 , yyScore: } ] but the yyScore line in the table is directly empty. I want 0 to be displayed by default when th...
< H1 > go straight to the code description < H1 > < H2 > before refresh < H2 > console.log(history.length); :1 history.replaceState(null,null, ?a=1 ); ?b=1 location.reload(); < H2 > after refresh < H2 > console.log(history.length); :...
modify the existing Excel file. Here use the openpyxl module . At present, the program opens a blank template Excel file and fills in the file, because the template contains such things as merging cells, but the program does not modify or manipulate mer...
when opened with the IE11 kernel like this, the page content is squeezed to the left, regardless of whether the compatibility mode is set to IE. but if the computer uses an IE8 browser, there will be no problem when it is opened. What is the reason...