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Master slave synchronization Note: the code in this article may involve misuse of Chinese characters, such as quotation marks and commas. Ask the paster to debug and modify the self code. Open the primary server mysql database configuration file Find my. In the mysql installation directory Ini configuration file, add under [mysqld] server-i ...

Insert query results into other tables Be able to write SQL statements that insert query results into other tables 1. Thinking At present, there is only one goods table. We want to add a commodity classification information. For example, the classification information of mobile devices cannot be added only through the goods table. How ...

summary Index is a data structure used by the storage engine to quickly find records. Through the rational use of database index, the access performance of the system can be greatly improved. Next, it mainly introduces the index types in MySql database and how to create a more reasonable and efficient index skills. Note: This is mainly for ...

Hive optimization is mainly divided into: configuration optimization, SQL statement optimization, task optimization and other schemes. Among them, SQL optimization may be mainly involved in the development process.The core idea of optimization is:Reduce the amount of data (such as partitioning, column clipping)Avoid data skew (e.g. adding param ...

4. Query 4.1 aggregate query 4.1. 1 aggregate function Common operations such as total statistics and average calculation can be realized by using aggregation functions. Common aggregation functions include: functionexplaincountReturns the number of queried datasumReturns the sum of the queried data. It is not a number. It is meaningles ...

Welcome to the MySQL technical articles shared by the great SQL community. If you have any questions or want to learn, you can leave a message in the comment area below. After seeing it, you will answer itIn the MGR test, after artificially creating the disk full problem, the node is OO m killedProblem descriptionIn MySQL 8.0 26 vs GreatSQL 8.0 ...

Chapter 6 SQL aggregate function JSON_ARRAYAGG An aggregate function that creates an array of JSON formatted values. Note: IRIS is available, and previous versions of IRIS are not available. outline JSON_ARRAYAGG([ALL | DISTINCT [BY(col-list)]] string-expr [%FOREACH(col-list)] [%AFTERHAVING]) parameter ALL - optional - specify JSON_A ...

Database application concept What is a database In short, it is a warehouse for storing and managing data. Common databases are divided into: Relational database, Oracle, MySQL, SQLServer, AccessNon relational databases, MongoDB, Redis, Solr, ElasticSearch, Hive, HBase Relational and non relational The early developed databases were b ...

preface In the use of Mybatis, for database operations, we create a corresponding interface and sql mapping file for each table. Note that our dao interface is not directly used in the code in the above two articles. The following will introduce two uses of dao interface. Tip: the following is the main content of this article. The followi ...

catalogue 1. Overview of stored procedures and functions 2. Create stored procedure 3. Call stored procedure 4. View stored procedures 5. Delete stored procedure 6. Grammar 6.1 variables 6.2 if condition judgment 6.3 transfer parameters 6.4 case structure 6.5 while loop 6.6 repeat structure 6.7 loop statement 6.8 leave state ...