Programmer Think

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 ...

Tip: after the article is written, the directory can be generated automatically. Please refer to the help document on the right for how to generate it preface I saw it on the bus in the morning**_ The article on MySQL binlog written by yidianyu * * in Jiangnan is very detailed about the use of binlog to recover the database. I can under ...

Welcome to my blog 1, Relational database < "\ 1 / >, data model There are three types of relationships between entities: The first mock exam model (1*) One to one Relational model uses two-dimensional tables to represent data and data relations. It is the most widely used data model. At present, various commonly used databa ...

Configure Druid The database connection pool is responsible for allocating, managing and releasing database connections. It allows applications to reuse an existing database connection instead of re establishing one. It releases the database connection whose idle time exceeds the maximum idle time to avoid database connection omission caused b ...

concept Master slave replication refers to copying data from one Redis server to other Redis servers. The former is called master / leader and the latter is called slave / follower. Data replication is unidirectional and can only be from master node to slave node. Master mainly writes, Slave mainly reads. By default, each Redis server ...

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 ...

Please read carefully and refer to the README document for the latest steps, processes and related requirements for the overall upgrade of Oracle 19c rac cluster from 19.3 opatch to 19.10. 1, View the current database patch version col ACTION for a8 col status for a15 set line 999 col ACTION_TIME for a30 col DESCRIPTION for a50 SQL> selec ...

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 ...

preface Today, I will share five data structures of Redis and their use scenarios in actual combat 1, Redis data structure? We all know that redis is an indispensable middleware tool in large-scale systems. It can support high concurrency scenarios or distributed locks. This is inseparable from his design architecture and underlying ...

1, Introduction (please skip those who don't want to see) Concept: redis is a high-performance NOSQL series non relational database What is Redis? Redis is an open-source high-performance key value database developed in C language. It officially provides test data. 50 concurrent 100000 requests are executed. The reading speed is 110000 ti ...