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Introduction to the author Author: Lucifer Liu, member of China DBA Alliance (ACDU).At present, he is engaged in Oracle DBA and has been engaged in Oracle database development, mainly serving manufacturing, automotive finance and other industries.Now it has Oracle OCP and OceanBase OBCA certification, and is good at Oracle database operatio ...

24.23 total / statistical function 24.23.1 count   --How many students are there in a class?   --How many students have statistical mathematics scores greater than 90?   --How many people have a total score of more than 250?   --Difference between count(*) and count (column) --Explanation: count(*) returns the number o ...

In the student information management system, firstly, the administrator will add, delete, modify, search and import teacher information, and then the teacher interface will log in to different teacher categories. The counselor teacher is responsible for adding, deleting and searching the relevant information of students, the educational adm ...

1. Prepare table information 2.MySQL advanced statement 2.1 alias Field alias, table alias Syntax: SELECT "table alias" "Field 1" [AS] "field alias" FROM "table name" [AS] "table alias"; Example: select A.age 'Age' from REGION A order by Age asc; 2.2 sub query: join table Insert ...

The real power of MyBatis lies in its statement mapping, which is its magic. Because of its extraordinary power, the XML file of the mapper is relatively simple. If you compare it with JDBC code with the same function, you will immediately find that nearly 95% of the code is saved. MyBatis is committed to reducing the use cost and enabling user ...

Log management MySQL log default save location /usr/local/mysql/data Error log It is used to record the error messages that occur when MySQL is started, stopped or running. It is enabled by default log-error=/usr/local/mysql/data/mysql_error.log #Specify the save location and file name of the log General query log It is used ...

AskTUG.com # technology Q & a website is believed to be familiar to everyone, but in addition to the familiar front-end pages, there is an unknown story behind the database supporting its operation. This paper is written by asktug Wang Xingzong, one of the authors of www.Discourse.com, shared the secret with asktug, which was born in Discou ...

0 storage engine introduction myisam storage: if the table does not have high transaction requirements and is mainly query and addition, we consider using myisam storage engine, such as posting table and reply table in bbs Regular defragmentation is required (because the deleted data still exists): optimize table_ name; InnoDB storage: ...

" Elasticsearch is a real-time distributed search and analysis engine. Its bottom layer is built on Lucene. In short, Lucene has distributed functions by expanding its search capabilities. ES usually provides end-to-end log / search analysis together with the other two open source components Logstash (log collection) and Kibana (dashboard ...

1. Explanation of NoSQL (non relational database) Why use Nosql Big data age - > springboot + springcloud The beautiful era of stand-alone Mysql! In the 1990s, the number of visits to basic websites was small, and only a single database was enough. Bottleneck of the whole website: 1. If the amount of data is too large, one m ...