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First, let's introduce my What's the use of ini folder: my Ini is the configuration file used in the MySQL database. This configuration file will be read when the MySQL server starts. We can update the configuration by modifying this file. my. If the INI file does not exist, you can first look at my Is the INI file hidden under the ProgramData ...

Chapter 10_ Create and manage tables Lecturer: Shang Silicon Valley - Song Hongkang (Jianghu person: Master Kang) Official website: http://www.atguigu.com 1. Basic knowledge 1.1 a data storage process Storing data is the first step in processing data. Only by storing the data correctly can we process and analyze it effectively. Otherwise ...

MySQL command integration (II) De duplication of query results select distinct ... // Add the distinct keyword after select be careful The distinct keyword can only appear first of all fields join query classification According to grammar SQL92SQL99 According to the connection mode of the table Internal connection: equivalent conn ...

Query statement (DQL) 1.5. 1 simple query statement Syntax format: select field name 1, field name 2, field name 3 From table name; Tips: Any sql statement that ends with a semicolon sql statements are not case sensitive mysql> select Empno,ENamE from -> emp; +-------+--------+ | Empno | ENamE | +-------+--------+ | 7369 ...

  catalogue Create a process to raise 100 yuan for the designated employee. And output the wages before and after the rise. Query the name and salary of the specified employee, and use the out mode parameter value to pass it to the caller. Call by binding variables in the command window, and the related steps Create a stored procedure, que ...

0 - problem description SQL tests whether there is a value in a group of data. You want to generate a Boolean value according to whether a group of row records contain a specific value. Imagine an example where a student will take several exams over a period of time. Suppose he takes three exams every three months. As long as he has pas ...

1, Slow query log learning 1. What is slow query log? The slow query log of My SQL is a kind of log record provided by MySQL. It is used to record the statements whose response time exceeds the threshold in MySQL, specifically the statements whose running time exceeds long_query_time value, it will be recorded in the slow query log.long_ quer ...

catalogue 1. Primary key constraint Format 1: set when writing fields when creating a table Format 2: create a table in. Declare the primary key constraint after the column Format 3: after creating a table, modify the table structure and declare the columns as primary keys 2 . Unique constraint Format 1: set when writing fields when creat ...

Chapter 1 Introduction to SQL1.1. What is sqlSQL: Structure Query Language. (Structured Query Language), operate the database through SQL (operation database, operation table, operation data)SQL was determined as the American Standard of relational database language by American National Bureau of standards (ANSI), and later adopted as the inte ...

General operations in traditional JDBC programming: 1. Register the database driver class and specify the URL address, database user name, password and other connection information of the database2. Open database connection through DriverManager3. Create a Statement object through a database connection.4. Execute the SQL statement through the ...