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Download scripts for creating tables and inserting data Here, for your convenience, the data script has been prepared for you. Click the link below to download directly Create data table script: http://tianchi-media.oss-cn-beijing.aliyuncs.com/dragonball/SQL/create_table.sql Insert data script: http://tianchi-media.oss-cn-beijing.aliyuncs.com/ ...

tips • avoid falling into the swamp of 'definition' and 'concept', and try to understand it with intuition and natural cognition • intuitive understanding of algorithm ideas and processes > > details • it is recommended to use full time to learn and master at one time I Basic concept of graph (many to many logical str ...

1 windowing function The OVER clause is allowed only in the SELECT and ORDER BY processing phases Two sum()over() in a select cannot be dividedLogical order of sql execution: FROM,WHERE,GROUP BY,HAVING, SELECT ,OVER,DISTINCE, TOP,ORDER BYData scenario According to the above data, it is necessary to count how many customers wechat experts ...

Topic source The database development course recently arranged some sql topics, which ended up bald The title and mysql statement are as follows First question Write an sql statement to query the employees whose cumulative working hours exceed 1000, and the result returns the employee job number eno. select eno from works group b ...

It's a little smoother to brush the questions today than yesterday. I actually brushed three tree questions in one breath. Although I still have to refer to the problem solution from time to time, I can also think about how the backtracking is realized. It seems that it is useful to brush more questions. I hope to maintain high learning efficie ...

Chapter 56 SQL function $EXTRACT A string function that extracts characters from a string by position. outline $EXTRACT(string[,from[,to]]) parameter String - the target string from which to extract the substring.from - optional - the position of a single character in the target string, or the beginning of the range of characters to e ...

Today, I want to talk about the monitoring function in Druid. Druid database connection pool is believed to have been used by many small partners. Personally, I feel that Druid is a relatively successful open source project of Alibaba. Unlike Fastjson, Druid has always been excellent in all aspects. It has complete functions and is easy to use ...

In the previous article, we gave an overview of database knowledge:< Database overview >, this paper introduces some basic and commonly used SQLite database knowledge. SQLite Foundation SQL basic syntax insert INSERT INTO Table name (Column name 1,...) VALUES (Column 1 value,...); modify UPDATE Table name SET Column name 1= Colum ...

Stored procedures and functions MySQL supports stored procedures and functions from version 5.0. Stored procedures and functions can encapsulate complex SQL logic. Applications do not need to pay attention to the complex SQL logic inside stored procedures and functions, but simply call stored procedures and functions. 1. Overview of stored pr ...

catalogue 1, Why do I need multi table query? 🐟 Which city does an employee named "Abel" work in? 2, How to implement multi table query 1. Error of Cartesian product (cross connection) ① Wrong implementation ② Cause of error The query method of the table requires multiple conditions ① Join condition of two tables ② If a fiel ...