there has just been a problem with the online code. The reason is that order sorting is not used in sql, resulting in inconsistent results of each query. So what is the default collation for mysql without specifying order by? ...
I ve asked similar questions before, but I didn t make it clear how I developed it. And now I would like to continue to ask some questions I have seen recently. Let me first introduce my current development environment and some practices. I would like...
sql judges if exists to report an error when updating database data ifiu= "if exists (select food_rank from config_battle where food_rank= " + cb.getFood_rank () + ") " + update+ "else " + insert; update and insert are two separate sql statemen...
create a test database CREATE TABLE `test` ( -> `id` int(2) unsigned NOT NULL AUTO_INCREMENT, -> `x1` varchar(20) NOT NULL , -> `x2` varchar(20) NOT NULL , -> PRIMARY KEY (`id`) -> ) ENGINE=MyISAM AUTO_INCREME...
A locking read, an UPDATE, or a DELETE generally set record locks on every index record that is scanned in the processing of the SQL statement. The word index record is often seen in Mysql documents. Is it "index and record " or is there any othe...
Table relationship: question: how to query the data shown in the figure using native sql statements? expected data structure (the list item of the product appears as a nested object): { "category": [ { "id": 1,...
this is to get List < PortfolioMemberView > at the Dao layer, and I am in the public List<PortfolioMemberView> getPortfolioMemberViewByPid(Integer pid){ portfolioId System.out.print(pid); try { Session sessi...
problem description < H2 > (the question has been updated, please take a look at the following. Thank you) < H2 > Today, open the company s website and display a loading error. there are no back-end developers for the time being because the compan...
Table structure: create table test_tmp ( id int, log_time datetime, item varchar (10) ) create table test_d ( id int, name varchar (10) ) Test data: insert into test_d values (1, hh ); insert into test_d values (2, xx ); insert into test_...
< H2 > recently wrote a background management system based on springboot, which provides many interfaces to add, delete, modify and insert databases without manually creating any threads. I wonder if there will be problems if concurrency occurs < H2 ...
Database is mysql8 the self-increment id checked out by the following statement and the actual self-increment id of the table will not, select auto_increment from information_schema.tables where table_schema= test and table_name= product ; the ...
in recent days, I have been doing database optimization. Due to the relatively large amount of data, some of the problems encountered are a machine that can put paper towels and count the income of each machine. Now there is a table recording machine in...
there is a requirement that there is a city field in the MySQL table, and there are 200 cities under that field. Each time, 10 cities are extracted from this field in turn, such as the first 10 cities in the first extraction, 11 ~ 20 in the second extra...
problem description: there are three tables Table relationship description: the 1.category table holds the directory id and the name. The 2.category_product table stores the id,product_id of the category table corresponding to category_id and...
now there is a project, and the demand is too painful! the price of each type of vip, from vip1 to vip5, is different! there is a data table in the backend that stores vip type vip_type with vip type price (money) and grade (level) now users write...
situation: uncertain orders are generated every day suppose there are eight orders generated today id status 1 2 3 4 5 6 7 8 I use loops to change the status of these eight orders to "shipping " . question: how can I tu...
the project uses the SpringBoot framework, and the persistence layer uses the mybatis, database for the mysql, business table to contain a composite unique index of four fields. Batch insertion or deletion on this table requires no logical deletion. Whe...
when should I use a relational database and when should I use a non-relational database? ...
query statement as follows: select * from table where index column in (xx,yy,zz,.) expect it to trigger the index, but sometimes the index cannot be triggered when there are too many elements. what is the reason for this? ...
requirements are as follows: there are one or more databases that hold all kinds of user data, such as contract information, time, amount, and so on. now we are going to develop a background system to regularly extract data from the specified databa...
let arr1 = ["", "", "", ...] let arr2 = [{1: "", 2: "A", 3: "205"},{1: "", 2: "", 3: "220"}, ...] let arr = [] [ { "": "", ""...
problem description how to fit Xiaomi 8 s bangs screen the environmental background of the problems and what methods you have tried related codes Please paste the code text below (do not replace the code with pictures) @media only screen a...
function fibonacciCatch(num) { let cache = [1, 1]; (function fibonacci(n) { if(typeof cache[n] == number ) { return cache[n] } else { return return cache[n] = fibonacci(n - 1) + fibonacci(n - 2) } })(num - 1); ...
found a similar effect on the Internet: ...
is to use c:forEach to view the result set in the database on the jsp page. The background output has a value, and there is also a value in HTML, but it is not possible to put it in jquery. this is what it used to be: $( document ).ready( function() {...