Mysql Voting question transaction

you need to check to see if the user has voted, and if so, the data is not inserted, and if not, the data is inserted. Under the condition of concurrency, it is possible for users to query not voting at the same time, and then result in the insertion of multiple pieces of data.

is there any good solution for such a situation?
as far as we know, transactions using databases do not lock select, so transactions may not solve such problems?
is it possible that only select for update is available? Is there any mainstream method

Mysql

May.22,2021

user id and voting id can be combined with a unique key.

   consider locking during concurrency. Voting should not be locked. Will lead to the defeat of the vote. 
 1. You can use the queue to add voting information to redis, and then Synchronize to mysql. 
 2. The number of votes is a separate int field. Just count. 
 3. Read from redis to mysql memory. However, if there is not such a large amount of concurrency, it is recommended that you do not need to do so. 
 the summary process is as follows: 
 php-> queue-> redis-> mysql <-redis <-php <-user


										
												Previous: Ask how this css style adapts to the mobile end.
												                		Next: How to set up how many minutes it takes to finish reading the blog page?
                							
					
						
					
															
						
														
								Php mariadb sum divided by if there is no value, can NAN, be shown as 0?
								
$selectTip = $pdo->query("SELECT * FROM `tips_rate`
                WHERE `tip_id` =   ".$row[  id  ]."   "
              );
              $selecttotal = mysqli_num_rows($selectTip);
              $rate = $pdo->query("SELEC...
								
									
																														Mysqli
																				mariadb
																				php
																			
									
										Feb.26,2021
									
								
							
														
								What is the relationship between transactions at different levels of isolation?
								
 for example, the isolation level of transaction An is repeatable read  my understanding is that a read sql statement of transaction An is the same as the result repeated many times,  regardless of whether or not other transactions have changed the data ...
								
									
																														Database
																				mysql
																			
									
										Feb.26,2021
									
								
							
														
								About the problem of the sudden downmachine of the mysql master from one of the parties.
								
 I know that mysql master and slave have been configured, but I don  t know what to do if one of them dies: 
 1. If there is only one master and one slave, do you want to upgrade the master manually in case the master dies? (it seems that you can  t call...
								
									
																														Read-write-separation
																				master-slave-backup
																				master-slave-replication
																				mysql
																			
									
										Feb.26,2021
									
								
							
														
								SQL statement, JOIN multiple table join table query problem
								
 subject table, which can be understood as a classification table. The  course and source_book tables are associated with subject  now use the subject table as the main table to query how many courses and books are under this category. 

  query statemen...
								
									
																														Mysql
																				sql
																			
									
										Feb.26,2021
									
								
							
														
								Check-in function, data storage time, year, month, day, why use varchar
								
 do a check-in function 
`create_time` decimal(20,3) NOT NULL,
  `create_date_ymd` varchar(15) NOT NULL COMMENT     ,
  `create_date_ym` varchar(15) NOT NULL,
  `create_date_y` int(4) NOT NULL,
  `create_date_m` int(2) NOT NULL,
  `create_date_d` int(2) ...
								
									
																														Php
																				mysql
																			
									
										Feb.26,2021
									
								
							
														
								Mysql fetches segmented data before the current time
								
 as shown in the following figure  
 the current time is 16   41   00. I want to take this section of data every two hours. How should sql write ?
...
								
									
																														Mysql
																			
									
										Feb.27,2021
									
								
							
														
								How mysql queries specified data in multiple tables
								
 1. Problem description  assume that there are n game order tables in the database, and the table name is game_ [0-9a-z] + _ order. . It is known that there is an order number 18demo000001. How can we efficiently find out which game table this order is i...
								
									
																														Mysql
																			
									
										Feb.27,2021
									
								
							
														
								The optimization problem of group by sentence in mysql and how to find the train of thought
								
 I want to optimize a sentence about group by. I don  t know where to start. I want to find a train of thought .
 SELECT 
adv_id,
network_id,
SUM(re_click) AS clk,
SUM(deny_click) AS dny_clk,
SUM(re_conver) AS re_ins,
SUM(mat_conver) AS mat_ins,
SUM(def_...
								
									
																														Mysql
																				php
																			
									
										Feb.27,2021
									
								
							
														
								On the Database query Optimization of java programmers in interview
								
 background:  1. I am a java programmer  2. Recently interviewed for a senior development position  3. The previous project mainly used less oracle,mysql, and the companies interviewed basically used mysql  s  4. I am weak in the database  5. Recently, I...
								
									
																														Oracle
																				mysql
																				sql
																				java
																			
									
										Feb.27,2021
									
								
							
														
								Does mysql support whether the query condition is an object?
								 like this  SELECT * FROM material WHERE {key:value} limit 1 ...
								
									
																														Axios
																				node.js
																				express
																				php
																				mysql
																			
									
										Feb.27,2021
									
								
							
														
								MySQL statement to ask for help
								
 how does sql write from the database table to the display of the page? 
 requirement: the first-level classification needs sorting, the first-level classification shows its subcategories, and the subcategories also need sorting. 
 
 
...
								
									
																														Sql
																				mysql
																			
									
										Feb.27,2021
									
								
							
														
								The problem of computing sorting in mysql query
								
 check-in table: fields include  user id userid  check-in time signtime timestamp type int  check-in type type is divided into 0 and 1 for check-in and check-out, respectively. A user can sign twice a day, once check-in and one check-out. Check-in and ch...
								
									
																														Mysql
																			
									
										Feb.27,2021
									
								
							
														
								Why can I still insert null values when not null, is set in mysql?
								
 Table structure  
 
...
								
									
																														Mysql
																			
									
										Feb.27,2021
									
								
							
														
								Annotation invalidation of dao interface using mybatis @ CacheNamespace cache
								

  use mybatis to configure custom secondary cache. Using xml annotation can use  < cache type=  "com.test.dao.MybatisRedisCache "   >  to successfully use custom cache, but using  @ CacheNamespace (implementation = MybatisRedisCache.class)  on the dao i...
								
									
																														Java
																				spring
																				mybatis
																				redis
																				mysql
																			
									
										Feb.27,2021
									
								
							
														
								The correct limit and take in the Larave with () function
								
  
class essay extends Model
{
    public function comment()
    {
        return $this->hasMany(  App  comment  )
    }
}

  
class comment extends Model
{
    public function essay()
    {
        return $this->belongsTo(  App  essay  )
    }
}

...
								
									
																														Mysql
																				laravel
																			
									
										Feb.27,2021
									
								
							
														
								The time-consuming problem of batch storage of a large amount of data in Mysql:, why does the speed decline so fast when the amount of data is large?
								
 mybatis+mysql for java projects 
            int batchAmount = 20000;
            for (int startIndex = 0; startIndex < size; startIndex += batchAmount) {
                int endIndex = startIndex + batchAmount;
                endIndex = (endIndex &...
								
									
																														Mysql
																				java
																			
									
										Feb.27,2021
									
								
							
														
								Mysql master-slave server, master database build table slave database not Synchronize
								
 Master and Slave built by mysql5.6, the newly created table is not backed up to the slave library  master and slvae data can both correspond to 
 
 
 can  t the test library be automatically backed up to the slave library when establishing a master-slav...
								
									
																														Linux
																				mysql
																			
									
										Feb.27,2021
									
								
							
														
								PHP MYSQL loops to output a single piece of data sequentially
								
 I want to do a circular sequence to output pictures. Don  t know how to write this code? 
  Table structure  
  
 for example, now the field ID of key=1 is 1, 2, 5, 7, 10, 11, 6 fields 
 I want to output one at a time in order. 
 output id 1 field for t...
								
									
																														Php
																				mysql
																			
									
										Feb.27,2021
									
								
							
														
								Is it convenient to modify data items when there is a lot of data in the mysql enum type?
								 for example, if the database has a field type of enum (  axiomagementific database  ), can you change this field to enum when there are millions of data in the database? will it be slow? ...
								
									
																														Mysql
																				sql
																			
									
										Feb.28,2021
									
								
							
														
								Please help me convert this native SQL statement into TP5 thank you!
								 ask God to help me translate this native SQL statement into TP5 thank you! It is Db:: (  name  )-> this kind of chained operation    select a.id, a.titlerect a. Createwriting time as answer_count from fa_question a. Isometric solvepaper count (b.qid) as ...
								
									
																														Thinkphp5
																				mysql
																				php
																			
									
										Feb.28,2021


				
					
						
	
						
		css
		mysql
		arrays
		josn
		react
		html
		typescript
		webpack
		npm
		sass
		R
		objective-c
		.net
		sql-server
		jquery
		python-3.x
		angularjs
		django
		angular
		excel
		regex
		iphone
		ajax
		linux
		xml
		pandas
		vba
		spring
		database
		wordpress
		string
		wpf
		xcode
		windows
		bash
		postgresql
		oracle
		multithreading
		eclipse
		list
		firebase
		algorithm
		macos
		forms
		image
		scala
		visual-studio
		azure
		bootstrap
		spring-boot
		react-native
		python-2.7
		docker
		performance
		function
		winforms
		matlab
		powershell
		apache
		dataframe
		api
		sqlite
		numpy
		rest
		shell
		selenium
		flutter
		dart
		maven
		loops
		qt
		swing
		android-studio
		csv
		express
		file
		class
		tensorflow
		sorting
		codeigniter
		perl
	
						MySQL Query :  SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5 
 MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e9e103-19a5.MAI); waiting for someone to free some space... (errno: 28 "No space left on device") 
 MySQL Errno : 1021 
 Message :  Disk full (/tmp/#sql-temptable-64f5-1e9e103-19a5.MAI); waiting for someone to free some space... (errno: 28 "No space left on device") 
Need Help?