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...
look at the documents on the official website and see that the following two sentences are incomprehensible. Please give me List Lists are mutable sequences, typically used to store collections of homogeneous items (where the precise degree of similar...
the time query is mentioned separately on the document, and after a general look, it is queried using the built-in method . this bothers me a lot when I use arrays to assemble query conditions. my query conditions look like this: $whereMap = [ [ n...
one of my projects is like this app (application) login (library application) in login , I use the R2 value generated by butterknife , similar to R2.layout.login , which is copied and modified into a constant ( fainl ) from the R file of ...
when using routing to switch pages, such as A page to B page, if the A page scrolls down, the B page is also scrolling distance when it is routed to B, how to get back to the top of the page each time you switch ...
-sharpinclude<malloc.h> -sharpinclude<stdio.h> -sharpinclude<stdlib.h> void init(int *p) { p=(int *)malloc(sizeof(int)); } int main() { int *p; init(p); *p=4; printf("%d",*p); return 0; }...