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1. Get to know MySQL preface Data needs to be stored. Large companies will go to IOE for self research! Database is the core existence in the software system -- DBA database administrator Java EE: Enterprise Java Web Development Front end (page: display, data) Background (connection point: connect database JDBC, link the front end (cont ...

1. Mapper CRUD interface The universal CRUD encapsulates the BaseMapper (opens new window) interface, which automatically resolves the entity table relationship mapping when Mybatis plus starts, and transforms it into the Mybatis internal object injection containerGeneric T is any entity objectWrapper updateWrapper entity object encapsulat ...

Mybatis study notes This article is to watch the UP master crazy God of station B say about Video of Mybatis explanation , reference Official documents of Mybatis And CSDN bloggers Black heart white lotus Personal Mybatis notes sorted out by relevant articles. Due to the author's limited ability, there are inevitable mistakes in the article. Y ...

preface sql tuning is very common in actual development, especially when the server is under pressure, it is necessary to optimize the time-consuming and commonly used sql to improve the high availability of the server. The explain tool will be used during tuning. This chapter will use explain to see how powerful it is. 1, EXPLAIN Us ...

MySQL Data Add Statement After the database and tables have been created successfully, you need to insert data into the tables in the database. In MySQL, you can use INSERT statements to insert one or more rows of tuple data into tables that already exist in the database. Basic Grammar The INSERT statement has two syntax forms, INSERT ...

1, Background introduction When the number of MySQL database instances of the group reaches 2000 + and the scale of MHA cluster reaches hundreds, the timely and efficient management of MHA is a challenge that DBA s must face. MHA cluster node information and operation status are the basis of management. This section mainly introduces how to col ...

MyBatis 1, Framework overview 1. Three tier architecture Interface layer: deal with users, accept user request parameters and display processing results. (jsp，html，servlet)Business logic layer: accept the data transmitted by the interface layer, calculate logic, call the database and obtain data.Data access layer: it is to access the datab ...

explain analysis execution plan You can use the EXPLAIN or DESC command to obtain information about how MySQL executes the SELECT statement, including how tables are connected and the order of connection during the execution of the SELECT statement. Execution plan of query SQL statement: explain select * from tb_item where id = 1;   ...

Simple redis distributed lock Locking: set key my_random_value NX PX 30000 This command is better than setnx because the expiration time can be set at the same time. If the expiration time is not set, the application hangs and cannot be unlocked, so it is locked all the time. Unlock: if redis.call("get",KEYS[1])==ARGV[1] then ret ...

Red hat RHCE exam am - RHCSA (RH134) serverb.example.com task 17. Set the expiration time of new user password Task requirements When creating a new user, the default password policy is set to expire after 20 days. Complete step Find login file cat /etc/login.defsAdjust the password expiration time in about 25 lines. The default is 99999 ...