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2021SC@SDUSC summary Last time, the TOAST mechanism of postgreSQL was analyzed. The TOAST mechanism belongs to the automatic processing mechanism of postgreSQL for variable length variables (big data), and can not handle blob s and clob s, which are large objects actively used by users. To deal with such large objects, you need to use anot ...

Hello, everyone. I'm Mr. Tony, who only talks about technology and doesn't cut his hair. Recently, a friend shared that he participated in the internship interview of data analyst of an Internet (live delivery) company. The following is my analysis of relevant SQL test questions. The database used is MySQL 8.0. If you find the article useful, ...

SQL basic knowledge sorting select query results, such as:   [student number, average score: group function AVG (score)] from which table to find data, such as: [related to grade: grade table score] where query criteria, such as: [b. course number = '0003' and b. score > 80] Group by grouping, such as: [average of each student: gro ...

1 what is a Graph The pictures introduced in this article are different from the common pictures in daily life. Generally, in English, in order to distinguish these two different graphs, the former is called Image and the latter is called Graph. In Chinese, the former will be emphasized as "picture", while the latter will be emphasiz ...

1. Stored procedures and stored functions      1. Stored procedure and stored function: MySQL provides the mechanism of stored procedure and stored function. Let's collectively call stored procedure and stored function stored programs. Unlike ordinary SQL statements, which need to be compiled first and then executed immediately, ...

Students of background development and operation and maintenance are certainly familiar with MySQL backup. Regular online database backup is necessary, and this process is generally automatic. This paper will introduce a shell script, which has the function of automatically backing up MySQL and automatically clearing expired backup data Back ...

preface When building a mysql Cluster, a single master makes master-slave replication, which greatly improves the reading and writing ability of the database, but once a single point of failure occurs, the whole cluster will be paralyzed. Therefore, we usually configure the master to improve the redundancy ability of the cluster. 1, W ...

Welcome to personal blog http://www.jkraise.top This case project is based on MySQL and Redis in the dark horse headlines Database optimization 1. Slicing2. Vertical split3. Horizontal split Slice effect Sharding is also called data sharing. Its main work is to split a single database and a single table. Multiple databases and tables toge ...

catalogue 1, Sort by keyword 1. Single field sorting 2. Multi field sorting 2, Or / and Application 3, Query non duplicate records 4, Group results 5, Limit result entries 6, Set alias Usage scenario 7, Join statement 8, Wildcard 9, Subquery 1. Definition 2. Subquery - alias 3. Subquery - exists 10, View 11, NULL value 1. Defi ...

MySQL built-in constraints and functions 1. Table constraints In order to ensure that the database is inserted according to the specified rules, table constraints are introduced in the database. Common table constraints are The primary key constraint primar key (cannot be empty or duplicate) if it is an integer type, it is generally defined ...