• MySQL must know and know


    1. Understand SQL A database is a container (usually a file or group of files) that holds organized data. A table is a structured list of a particular type of data. Schema information about the layout and characteristics of databases and tables. Column a field in a table. All tables consist of one or more […]

  • In depth analysis of regular expressions and wildcards


    1. Special symbols ”      What you see is what you get“”      Special symbols are parsed and run“      == $ () run the command inside first and leave the result>      Redirection symbol         First empty the contents of the file, and then append the last part of the file>>     Append redirection […]

  • Elasticsearch7.6.2 – rest complex query


    Then, in the previous article, query complex query is performed must This relationship, equivalent to and, must be satisfied at the same time    should This relationship is equivalent to or. Just meet one   Three pieces of data were found here must_not   must_ Not quite so! So one piece of data is found […]

  • Let’s encrypt – use free SSL / TLS certificates


    Free SSL certificates are provided by domestic cloud service providers such as Alibaba and Tencent, but their certificates are only free for one year, and do not support free wildcard certificates. The charged certificates are at least 1K / year, which is certainly unbearable for individual users. Fortunately, we still have themLet’s Encrypt。 adoptLet’s EncryptAlthough […]

  • MySQL Basics (I)


    The main content of this paper is the basic statements of MySQL and regular expressions. Personal GitHub exists in the database content operated in this article:https://github.com/YuanGao-1/blog_demo.git init_ Schema.sql is a table creation script init_ Data.sql is the test data The specific import process is as follows: Create database (database name); Use (database name); source init_ […]

  • Springboot ehcache configuration and usage


    POM introduces dependency <!– Ehcache –> <dependency><groupId>net.sf.ehcache</groupId><artifactId>ehcache</artifactId></dependency>2. Put a file ehcache.xml directly in the resources directory <ehcache xmlns:xsi=” xsi:noNamespaceSchemaLocation=” updateCheck=”false”> <diskStore path=”java.io.tmpdir”/> <!– Defaultcache: default cache policy of echcache — > <defaultCache maxElementsInMemory=”10000″ eternal=”false” timeToIdleSeconds=”120″ timeToLiveSeconds=”120″ maxElementsOnDisk=”10000000″ diskExpiryThreadIntervalSeconds=”120″ memoryStoreEvictionPolicy=”LRU”> <persistence strategy=”localTempSwap”/> </defaultCache> <!– Menu cache policy — > <cache name=”menucache” maxElementsInMemory=”10000″ eternal=”false” timeToIdleSeconds=”120″ timeToLiveSeconds=”120″ maxElementsOnDisk=”10000000″ […]

  • Android Foundation Series (1) Java generics


    sketch Java generics is a new feature introduced in j2se1.5. Its essence is parameterized type. That is to say, the operated data type is specified as a type parameter. This parameter type can be used in the creation of classes, interfaces and methods, which are called generic class, generic interface and generic method respectively.Let’s understand […]

  • MySQL regular expression like wildcard


    Some characters of extended regular expressions are: “. matches any single character.A character class “[…]” matches any character within square brackets. For example, “ABC” matches “a”, “B” or “C”. To name a range of characters, use a “-“[ A-Z] “matches any lowercase letter, and” [0-9] “matches any number.“*” matches zero or more things in front […]

  • Linux search command summary – where is, which, locate, find, grep


    1、 Command search commandwhereisAndwhich 1. Where is command Search the path of the command and the location of the help document option -b: Find only executable files -m: Search for help files 2. Which command Search command location and alias 3. Extension Whatis queries what functions a command performs 2、 File search commandlocate 1. Introduction […]

  • Examples of using wildcards in SQL Server


    In some cases, being familiar with the use of SQL Server wildcards can help us solve many problems simply. –Use_ Operator to find a three letter name ending with an in the person table USEAdventureWorks2012; GO SELECT FirstName, LastName FROM Person.Person WHERE FirstName LIKE’_an’ ORDER BY FirstName; —Use the [^] operator to find all people […]

  • Today’s knowledge sharing: SQL wildcard


      Wildcards can be used to replace any other character in a string. In SQL, wildcards are used with the SQL like operator. SQL wildcards are used to search for data in a table. In SQL, you can use the following wildcards:   Wildcard description %Replace 0 or more characters _ Replace one character Any […]

  • CentOS 7 MySQL 5.7 master slave only synchronizes partial libraries or tables


      There are two ways to synchronize partial data The master only sends the required data; Advantages: the relay log is small; if there are multiple slave databases, it only needs to be controlled in the master database Disadvantages: it’s troublesome to modify midway, and you can’t control the synchronized table Slave only receives what […]