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Basic operations of grid workers computers, basic operations of maxwell - mesh division
This article details how to perform efficient meshing in Maxwell and other electromagnetic field finite element software, including adaptive processin......
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What is computer system latency and what is low latency?
The article was browsed and read 9.5k times. Low latency refers to shorter time delays in computer systems or communication networks. It is usually ......
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How to index JSON fields in MySQL
This article introduces the method of indexing fields in JSON objects using virtual fields in MySQL 5.7. MySQL 5.7 supports JSON fields since 5.7.8, but does not provide the ability to index JSON fields directly. Through example data, the article shows the operation of adding virtual fields and adding indexes on them, which can improve the speed of JSON content retrieval....
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Mysql adds index to json
This article introduces how to support the addition of multi-value indexes on json columns since MySQL8.0.17, how to check versions, create and use multi-value indexes, and what to note when processing different types of data. The improvement in query performance before and after adding indexes is demonstrated through examples....
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【MySQL】MYSQL5.7 Create/modify virtual columns
The article was browsed and read 3.9k times. Create table: CREATE TABLE `Table name` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL COMMENT 'name', `attach` json DEFAULT NULL COMMENT 'JSON field', PRIMARY KEY (`id`)) ENGINE=MyISAM DE..._mysql Modify virtual fields...
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How to view application startup parameters under window system
The article was browsed and read 2.5k times. This article details how to use WMIC commands in the CMD console to view Java startup parameters and process information of specific PIDs. The example demonstrates how to combine the findstr command for information filtering to help readers understand the application of WMIC commands in depth....
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What are mysql virtual columns and application examples
The article introduces the virtual column characteristics in MySQL, including storage columns (STORED) and virtual columns (VIRTUAL). Stored columns are calculated and stored when inserted or updated, and can be indexed but occupy more space; virtual columns do not store values and are calculated dynamically during query, saving space but cannot be indexed. The article provides examples of creating and using these two virtual columns....
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Both CAST and CONVERT functions are used in MySQL for data type conversion
Both CAST() and CONVERT() functions in MySQL are used for data type conversion. Although these two functions are used interchangeably in most cases, there are slight differences between them_mysql cast...
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Row and column conversion in Oracle database
Row and column conversion in Oracle database includes CASE statements, PIVOT and UNPIVOT_oracle row conversion...
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Several methods of Oracle table association update
Oracle table association update_oracleupdate association update statement...
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What does the ‘virtual column’ in Mysql 5.7 do?
A very practical function virtual column is introduced in Mysql 5.7. Generated (Virtual) Columns. For its purpose, we use a scenario to illustrate that there is a table containing a column of date type `SimpleDate` dateSimpleDate is a commonly used query field and a date function needs to be executed on it, such as SELECT... WHERE dayofweek(Simpl_Virtual Column...
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Mysql Virtual Field_What does the ‘virtual column’ of Mysql 5.7 do?
A very practical function is introduced in Mysql 5.7. Virtual column Generated (Virtual) Columns. For its purpose, we use a scenario to illustrate suppose that there is a table containing a date type column `SimpleDate` dateSimpleDate is a commonly used query field and a date function needs to be executed on it, such as SELECT... WHERE dayofweek(SimpleDate) = 3...The question at this time is...What is the use of a virtual column of _navicat...
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Mysql virtual column
MySQL virtual column features and practical use_mysql virtual column...
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Linux docker runs exe, how to run windows in docker
The article was browsed and read 5.6k times. Let's learn about Docker in the Windows operating system and installing the Docker Windows client in it. The Docker engine uses Linux-specific kernel features and therefore cannot run through the Windows kernel. Therefore, (on Windows) the Docker engine creates a small virtual system to run Linux and utilizes its resources and kernel. In this way, the Windows Docker client can use this virtual Docker ..._docker to run exe...
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Check CPU power consumption under Linux system, and check CPU information under Linux system
The article has been viewed and read 6k times. View CPU information under Linux system View CPU information (model): # cat /proc/cpuinfo| grep name | cut -f2 -d: | uniq -c8 Intel(R) Xeon(R) CPU E5410 @ 2.33GHz (I saw that there are 8 logical CPUs, and I also know the CPU model) View the number of logical CPUs: #cat /proc/cpuinfo|grep "processor"|..._linux to view CPU power consumption...
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Docker overlay2 takes up a lot of disk space processing method
The article was browsed and read 7.6k times. When using docker, there is often insufficient disk space, and the usual reason for this problem is that......
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vue gets div tag_var method in vue
The article was browsed and read 7.4k times. 1. HTML DOMquerySelector() method According to the previous jq method, CSS selector obtains element tags [execute in the mounted method] document.querySelector obtains the first element of the selected element; document.querySelectorAll obtains all selected elements; eg: document.querySelector("#demo"); document.querySelec..._vue obtains the image tag in the div...
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Mybatis-plus query time-consuming and slow
The article was browsed and read 4.9k times. 1. Phenomenon: Find more than 30,000 ids and use EntityWrapper ew = new EntityWrapper<>(); ew.in(TableFieldConstant.F_AUTH_RESULT_ID, ids); query will be very slow 2 reasons followed mybatis-plus source code protected String formatSqlIfNeed(boolean need, String sqlStr, Object... params) { ..._mybaitsplus call time 7 seconds...
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python prime number (filter method) (simple prime number filtering method)
Prime numbers are prime numbers. The following are all expressed by prime numbers, also known as screening method. The specific method is: first arran......
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【MySQL8 lowered version to MySQL5.7】
The article was browsed and read 2.8k times. Mysql8.0's character set and sorting rules have been changed compared to 5.7. The table encoding is utf8......
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