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🔎 MySQL notes Retrieve data Retrieve different rows select distinct vend_id from products Limit the result, that is, limit the number of rows output select prod_name from products LIMIT 4,5 //Indicates that five rows of data are retrieved from the fourth row. The first is the starting position and the second is the number of rows to be r ...

sql execution statement flow analysis The whole processing flow is in exec_simple_query function. The code structure is as follows: /* * exec_simple_query * * Execute a "simple Query" protocol message. */ static void exec_simple_query(const char *query_string) { ... //Original syntax tree acquisition /* * Do basic parsing of the quer ...

prefaceIn actual project development, there are often functional development requirements for scheduled tasks. Scheduled tasks are mainly divided into two types,Execute a task at a fixed time, that is, TimerBased on a fixed time interval, a task is executed periodically, that is, TickerMany time-based scheduling frameworks are inseparable from ...

Author: Yanbo Qingyun technology database R & D EngineerAt present, he is engaged in the development of PostgreSQL products and is keen on the study and research of PostgreSQL databaseLast issue We introduced the PG cluster replication management tool repmgr, which can easily build a highly available cluster of PostgreSQL. After the primary ...

Hello, I'm the program ape pony, the hupiao family! Writing an article is a summary of ordinary times and everyone's common learning and progress, so as to code out their dreams as soon as possible 😊 Coordinates: subway station next to pony work 1. Cause of problem I believe that the development partners can't get around a proble ...

Java 12 does not have many useful features for developers, but it is practical.   String enhancement Java 12 further enhances string operations by adding two methods. String indent String indent(int n) indents the string according to parameter n. The specific rules are When n > 0, n spaces will be inserted at the beginning of each line ...

typora-copy-images-to: img 1, Dao interface proxy implementation 1.1 introduction to agent development mode The agent development method of Mybatis is adopted to realize the development of DAO layer, which is the mainstream of entering the enterprise later. Mapper interface development method only requires programmers to write map ...

Copy Set PrincipleThe role of replication setsIn order to achieve high availability of mongodb services, there is a master-slave relationship between replica setsQuickly copy data to other nodes when data is writtenAutomatically select a new node to replace the primary node when it failsWith the above features, if we know redis, we can quickly ...

Phase 2 ------------------------------------------------------------------------------- database 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, Access non relational database, MongoDB, Redis, Solr, ElasticSearch, Hive, HBase My ...

preface: Followed by the previous article. The above analyzes the whole process of the consumer sending the request, and finally sends the request to the Provider through NettyChannel. Of course, a series of processing has been carried out in the middle. From the perspective of Provider, this paper discusses how the service Provider handles t ...