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Topic: there is a student table, which records the courses and scores of all students in a class. Each student has multiple courses. Different students may take different courses. Try to write an SQL statement to find out the names of all students whose course scores are greater than 80.Table structure and data are as follows: - ...

For simple requirements, I found a complete project github: data can be migrated through configurationhttps://github.com/Lifedance/DataTransfer Thank you very much. But it's a pity that I can't use it in my project. It's estimated that the project is not perfect, or maybe it's for safety My table can never be written. But I can ...

Recently, an error "error: cannot fetch last explain plan from plan" was encountered. Therefore, the following scenarios were studied for details:     1: When you forget to use EXPLAIN PLAN in front of the SQL statement, and then use select * from table (DBMS? Xplan. Display) to view the execution plan of the specific SQL, you will en ...

background Colleagues described that the database orcl instance will be unable to connect in a period of time. It can be used after one restart. It will be unavailable again in about 30 minutes to an hour. Problem finding and troubleshooting ideas For oracle problems, first check the alert.log log View the alert.log log log ...

Each table has a main heap disk file in which most of the data is stored. If a table has columns that may be very wide (large in size), there is another TOAST file associated with the table, which is used to store values that are too wide to be stored in the main table. If you have this attachment file, there will be an index a ...

understand First, let's talk about why there is a ContentProvider? When an application wants to access the database of another application, because each application's database file is private and cannot be accessed directly, the accessed application needs an external database content provider, that is, content provider. &l ...

Source code: GitHub point here || GitEE point here 1, C3P0 connection pool 1. C3P0 introduction C3P0 is an open source JDBC connection pool. The application program initializes the database connection according to the C3P0 configuration, and can automatically reclaim the function of idle connection. 2. Core dependency <dependency> & ...

Open the link and display the following: Analysis: first of all, think of the problem that this may be to forge IP, and then use the HTTP header of forged IP (for example, x-forward-for, etc.). The forgery in burp is successful, as shown in the following figure: Response results: It is found that forgery can be successfully carried out ...

The so-called parallel execution refers to the ability to physically divide a large serial task (any DML, or general DDL) into several smaller parts, which can be processed at the same time. When to use parallel execution Parallel execution is essentially a non scalable solution designed to allow a single user or each specific SQL statement ...

When inserting data in Python, no error is reported, but no newly added data appears in the database Reason: the commit operation is missing. Solution: when Python operates the database, if the data table is modified / deleted / added, the system will save the operation in memory. Only when commit() is executed, the operation ...