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After mysql 5.7, the processing of group by is different. Here we do some research based on a demo. Official documents: https://dev.mysql.com/doc/refman/5.7/en/group-by-handling.html https://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_only_full_group_by   demand Statistical user login times, display user Id and name, as follows ...

Recently on the project, customers asked me to help see a view with slow queries, provided that they had optimized it internally before giving it to me. When I saw their optimization, they simply used hint statements, and it didn't work. First of all ...

This article only describes IP, virtual IP and scan changes in the same segment of the public network, and will introduce IP changes in different segments later. The experimental environment: 1. Stop RAC Cluster Services Cluster services are stopped at two nodes: [root@odb09 ~]# /u01/app/11.2.0/grid/bin/crsctl stop cluster -all [root@odb09 ~] ...

I recently received a task, to climb a data, the data in a web page table, the amount of data hundreds. Open debugging mode and find that the interface returns an html page, as long as it is treated as string. (xpath crawler is troublesome for parsing html files) The scheme uses regular matching of all cell rows and extracting cell content, whi ...

In Mobile, there are three locations where the parameter "useGeneratedKeys" can be set: 1. Set the useGeneratedKeys parameter in the setting element. For databases that support automatic generation of primary keys, such as mysql, sql server ...

Monitoring tool DPA found a DB Commit Time indicator alarm on an Oracle database server overseas, which exceeded the red alarm line (about 40 milliseconds, yellow alarm 10 milliseconds, red alarm line 20 milliseconds). As shown in the following screenshot, the AWR report for the corresponding period was generated, and log file sync waited insid ...

problem A strange problem with a project recently is that the database often reports that the connection is closed every few hours. Even with the following configuration, it is still not possible, and there is no article on the Internet explaining the pit. test-on-borrow: true test-while-idle: true validation-query: select 1 from dual Trou ...

Author: Yang Taotao background Today's article comes from a question asked by today's customers. Problem: I'm migrating from Oracle to MySQL, and the data has been converted to a simple INSERT statement. Because there are many statements, I don't know how to locate the wrong statement every time I import it. If there are fewer INSERT statement ...

The following kernel parameters need to be configured when installing the database: fs.aio-max-nr = 1048576 fs.file-max = 6815744 kernel.shmall = 2097152 kernel.shmmax = 4294967295 kernel.shmmni = 4096 kernel.sem = 250 32000 100 128 net.ipv4.ip_local_port_range = 9000 65500 net.core.rmem_default = 262144 net.core.rmem_max = 4194304 net.core.wm ...

Student Comprehensive Evaluation System Creation Statement of mysql Database in Student Comprehensive Evaluation System Creating sentences of oracle database in students'comprehensive evaluation system SQL Server database creation statement of st ...