How does MySQL calculate the difference of a certain column in two adjacent rows
MySQL calculates the difference between two adjacent rows of a certain column: First, use [r1.rownum = r2.rownum – 1] to determine whether the two records are consecutive rows; then use the TIMEDIFF function to calculate the time difference That’s it. 【Related learning recommendation: mysql tutorial(video)】 MySQL calculates the difference between two adjacent rows and a column: First, the blogger has a table on the server side to record the GPS reported by the driver Point information, the table structure is as follows: — driver GPS collection table CREATE TABLE captainad_driver_gps_position ( id BIGINT NOT NULL auto_increment COMMENT ‘primary key’, business_id BIGINT DEFAULT NULL COMMENT ‘Business ID’, device_mac VARCHAR (64) DEFAULT NULL COMMENT ‘Device MAC address’, device_imei VARCHAR (64) DEFAULT NULL COMMENT ‘Device IMEI’, lat_lng VARCHAR (64) DEFAULT NULL COMMENT ‘latitude and longitude’, capture_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP COMMENT ‘capture time’, create_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP COMMENT ‘Create Time’, update_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT ‘Modify time’, PRIMARY KEY (id), KEY `idx_business_id` (`business_id`) USING BTREE ) ENGINE = INNODB DEFAULT CHARSET = utf8 COMMENT = & # 39; driver GPS collection & # 39;; The data recorded in the table is roughly as follows: Click to get GPS now After the…
Mysqlcsv Chinese garbled how to do
mysql php Write your review! Spit it out, see everything Member Login | User Registration recommended reading install Complete actual combat to configure the server from scratch (1) Hardware preparation A HPProLiantDL160G5 server (hard disk expanded to 480G) a personal computer (window… [detailed] Crayon Shinchan 2023-08-26 13:43:53 io Java project: Springboot library management system Author’s homepage: Ye Weiyang 5788 Introduction: High-quality creators in the Java field, Java projects, learning materials, technical mutual assistance Get the source code at the end of the article… [detailed] Crayon Shinchan 2023-08-26 13:43:40
How to deal with garbled Chinese characters when storing data in mysql
The solution to Chinese garbled characters when mysql saves data: 1. Set the code set related to the client [set names gbk;]; 2. In the [my.ini] configuration file, set [default- character-set=utf8] to 【=gbk】, and restart. The above is the detailed content of how to deal with Chinese garbled characters when mysql stores data. For more information, please pay attention to other related articles on 1024programmer.com!
How does mysql delete duplicate records in the database?
The steps for mysql to delete duplicate records in the database: first count duplicate data; then use the “SELECT DISTINCT” statement to filter duplicate data; finally add INDEX and PRIMAY KEY to the data table to delete duplicate records in the table . For regular MySQL data tables, there may be duplicate data. In some cases, the existence of duplicate data is allowed, and in some cases, it is not allowed. At this time, we It is necessary to find and delete these duplicate data, the following is the specific processing method! Related learning recommendation: mysql tutorial (video) Method 1: Prevent Duplicate data appears in the table When no data is added to the table, you can set the specified field in the MySQL data table as PRIMARY KEY (primary key) or UNIQUE (*** ) index to ensure the uniqueness of the data. For example, in the student information table, the student number no is not allowed to be repeated, the student number no needs to be set as the primary key, and the default value cannot be NULL. CREATE TABLE student ( no CHAR(12) NOT NULL, name CHAR(20), sex CHAR(10), PRIMARY KEY (no) ); Method 2: Filter and delete…
How to export mysql database table to excel
mysql php Write your review! Spit it out, see everything Member Login | User Registration recommended reading case MySQL InnoDB four transaction levels and dirty read, non-repeated read, phantom read_MySQL MySQLInnoDB transaction isolation level dirty read, repeatable read, phantom read MySQLInnoDB transaction isolation level has four levels, the default is repeatable read (REPEATABLE READ). · Read uncommitted (READUNCOM… [detailed] Crayon Shinchan 2023-08-26 13:36:59 ip zabbix introduction and installation Introduction: The article is divided into 3 paragraphs 1. Zabbix introduction, including architecture, component workflow, etc. 2.zabbix installation, yum installation and compilation installation 3.zabbix… [detailed] Crayon Shinchan 2023-08-26 13:29:24
What is the difference between mysql synchronous replication and asynchronous replication?
Differences: 1. Asynchronous replication means that the Master writes events into the binlog. It does not know whether the slaves receive or process them. It cannot guarantee that all transactions are received by all slaves. 2. Synchronous replication means that the Master submits transactions until The transaction completion information will be returned to the client only after all slaves have submitted the transaction. Related learning recommendation: mysql tutorial (video) mysql synchronous replication and asynchronous replication The difference: Asynchronous replication MySQL replication is asynchronous replication by default. Master writes events to binlog and commits transactions. It does not Know whether the slave receives or not; Disadvantage: It cannot guarantee that all transactions are received by all slaves. Synchronous replication Master submits the transaction, and will not return the client transaction completion information until the transaction has been submitted in all slaves; Disadvantage: There may be a delay in completing a transaction. Semi-synchronous replication When the semi-synchronous replication function is enabled on the Master, at least one slave should enable its function. When the master submits a transaction to the slave, and the transaction has been written into the relay-log and flushed to the disk, the slave will notify the master that…
What is the maximum value statement of mysql query
Mysql query maximum value statement is: first group stuname field; then use MAX function to calculate the maximum value in each group, the code is [SELECT a.stuname,MAX(a. score) AS..]. 【Related learning recommendation: mysql tutorial(video)】 Mysql query maximum value statement is: 1, method 1 SELECT a.stuname,MAX(a.score) AS score FROM stuscore a GROUP BY a.`stuname` ; In this statement, we group by stuname field and then use MAX() The function calculates the maximum value in each group. 2. Method 2: use connection SELECT a.stuname,a.score AS score FROM stuscore a JOIN stuscore b ON a.`stuname`=b.`stuname` GROUP BY a.`score` HAVING a.`score`=MAX(b.`score`); In the second sql statement, we use stuname as the judgment condition to perform two table Connection operation. If only execute SELECT a.stuname,a.score AS score FROM stuscore a JOIN stuscore b ON a. stuname=b.stuname We will get the following result set: The above is the detailed content of the mysql query maximum value statement, more Please pay attention to other related articles on 1024programmer.com!
What should I do if mysql fails to set log-bin?
The solution to the failure of mysql to set “log-bin”: first modify the [my.cnf] file; then store the log file in binary form; finally find the binary file and use the command to export it. 【Related learning recommendation: mysql tutorial(video)】 The method to solve the failure of mysql to set log-bin: 1. Modify the my.cnf file log-bin=mysql-bin binlog_do_db=hello log-bin: Setting this parameter means enabling the binlog function and specifying the path name binlog_do_db: Specify the database name for logging After modifying the file, you need to restart the database service 2 . The log file exists in binary form, find the binary file, and use the command to export a) Find the storage location of the binary file [root@CCDT-gluster-1 mysql]# ps -ef | grep mysql root 12017 1 0 13:45 pts/0 00:00:00 /bin/sh /usr/bin/mysqld_safe –datadir=/home/Mysql/MysqlData –pid-file=/home/Mysql/MysqlData/mysql1. pid mysql 12336 12017 0 13:45 pts/0 00:00:02 /usr/sbin/mysqld –basedir=/usr –datadir=/home/Mysql/MysqlData –plugin-dir=/usr/lib64/mysql/ plugin –user=mysql –log-error=/home/Mysql/MysqlData/CCDT-gluster-1.err –pid-file=/home/Mysql/MysqlData/mysql1.pid root 14080 26031 0 13:50 pts/0 00:00:00 grep mysql root 20668 1 0 May11 ? 00:00:00 mysql -u root -p b) The binary file is stored in the directory where the database file is located, use the mysqlbinlog command to export [root@CCDT-gluster-1 mysql]# cd /home/Mysql/MysqlData [root@CCDT-gluster-1 MysqlData]# mysqlbinlog…
How to remove the mysql service?
How to remove the mysql service: 1. Go to “Control Panel->Program->Uninstall or change the program” and delete the mysql program; 2. Delete the [my.ini] file under the MySQL folder, If the backup is good, you can delete all the folders directly; 3. Enter the registry and delete the relevant MySQL directory. Related learning recommendation: mysql tutorial (video) Remove the mysql service Method: 1. Delete in the add delete program in the control panel 2. Delete the my.ini file under the MySQL folder. If the backup is good, you can Delete all folders directly 3. Start->Run->regedit to see if these places in the registry have been deleted HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services \Eventlog\Application\MySQL directory deletion HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\Eventlog\Application\MySQL directory deletion HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog\Application\MySQL Delete the directory (I didn’t find it when I uninstalled, and I still achieved the purpose of completely uninstalling after skipping it.) 4. This one is very important C:\Documents and Settings\All Users\Application Data\MySQL There are also MySQL files here, which must be deleted Note: Documents and Settings Where is it? 1. Turn on the computer, open the C drive, select the [Organization] menu – folder and search options; 2. Select [View], remove the [Hide protected operations Check in front of System File], confirm; 3. At this…
How does mysql delete multiple table database data
How to delete database data in multiple tables in mysql: first establish a cascading delete relationship between two tables; , delete the related data in another table at the same time. The above is the detailed content of how mysql deletes multiple table database data. For more information, please pay attention to other related articles on 1024programmer.com!
