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catalogue multi-table query multi-table query introduce: SELECT..... FROM... WHERE...AND/OR/NOT ORDER BY...(ASC/DESC) LIMIT... Which city does the employee named 'Abel' work in? SELECT * FROM employees WHERE last_name='Abel'; SELECT * FROM departments WHERE department_id=80; SELECT * FROM locations WHERE location_id=2500; 2. How to ...

1, The mysqldump command backs up data MySQL provides a convenient tool mysqldump for exporting database data and files from the command line. We can export database contents directly from the command line. #MySQL dump common mysqldump -u root -p --databases Database 1 database 2 > xxx.sql 2, mysqldump common operation examples 1. Back ...

Some optimizations have been made for Struct in. NET6. Let's take a look at the optimizations for Struct in. NET6 through some cases. 1, Record Struct Although there was a record in the previous version, the record in the previous version is a class and a reference type, but the record struct is a value type and a structure. Its usage is as f ...

Basic SELECT statement 1, SQL overview 1. SQL background In 1974, IBM researchers published a paper "sequence: a structured English query language", which unveiled database technology. Up to now, this structured query language has not changed much. Compared with other languages, the half-life of SQL can be said to be very long. S ...

Experiment 2: create and manage database Experimental content 1. Create database Assume that the SQL Server service has been started and log in to the computer as Administrator (the file name is customized); Please use the Management interface mode and T-SQL statement respectively to realize the following operations: It is required to create ...

📚 preface SQL language has a history of more than 40 years. Since it was applied, it has been almost everywhere. Every payment record we consume, every user information we collect and every message we send will be stored in the database or its related products, and the language to manipulate the database is SQL! SQL is almost a necessar ...

Chapter 1 Introduction to FastDFS FastDFS overall architecture Two institutions: client (usually our program) + server (tracker [scheduling] + storage node [file storage and management]) Chapter 2 Establishment of FastDFS environment Start tracker, storage and upload files fdfs_trackerd /etc/fdfs/tracker.conf fdfs_storaged /etc/fdf ...

1, Introduction to master-slave replication 1.1 what is master-slave replication Copy the binlog log of the master server to the slave server for execution to achieve the consistent state of the master-slave data, which is called master-slave replication. In a word, what the master database does is what the slave database does. 1.2 why s ...

Pay attention to official account and learn more knowledge summary sqlite is a relational database, so object relationship is an important part. For example, the data we define includes forests and trees, and forests contain trees. At this time, the defined forest should contain a tree object, which is the object relationship between forest ...

Note: the following will use the emp table in the mysql database in the mysql database management system as an example This content continues from the previous study notes: DQL statement 2 in SQL (learning note 3) 1, Grouping function Grouping function is also called multi line processing function, and there are only 5 multi line proce ...