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  View CREATE/ALTER/DROP VIEW ViewName as SELECT(...) You can continue to create a view based on it, that is, you can place the previously created view as a table name in the select statement of the new view Format data using views (that is, reassemble and stitch fields) CREATE VIEW View_player_team AS SELECT CONCAT(player_name, '(' , t ...

Sometimes we need to save a lot of data, which is time-sensitive, such as some logs. After a period of time, the existence of these data is not significant, and in addition to taking up a lot of hard disk space, it may make data queries slow.This data needs to be cleaned up regularly.We can cope with ...

Adding fields to a table of ten million or more levels in MySQL has always been a headache. In this case, how to deal with it? This paper uses three common scenarios to illustrate the case. 1. Environmental preparation Database version: 5.7.25-28 (Percona branch) Server configuration: three centos 7 virtual machines with 2CPU 2G memory Database ...

Database integrity: prevent non semantic and incorrect data from entering the database; Database security: prevent illegal users from intruding into the database and illegally accessing the database data. 5.1 entity integrity PRIMARY KEY Entity integrity definition: single attribute - column level, tabl ...

Database security and transaction operation Article catalog Database security and transaction operation 1, Purpose and requirements 2, Experiment content 1. Design the security mechanism so that the user Wang Ming can only find the staff of the financial department 2 design a role_Emp ", this ...

1, Introduction to cursors 1. Introduction to cursors Cursor is a database query stored on MySQL server. It is not a select statement, but a result set retrieved by the statement. With the cursor, the result set can be processed row by row conveniently. The design of cursors is the idea of data buffer, which is used to store the results of S ...

The serial number recorded in the table is usually done by the method of sequence. Sometimes it needs to be reset in the creation project, such as in the creation stage, test stage, etc. we can reset the sequence in various ways, delete the reconstruction, sequence reset, etc. The following is an example of a stored pro ...

catalog Create tableUpdate tableDelete tableQuery table structureCreate view Create table Create table TestSql CREATE TABLE TestSql( Id bigint identity(1,1) not null PRIMARY key ) reference material SQL CREATE TABLE statementSQL PRIMARY KEY constraint Update table Create field Create a normal field --ALTER TABLE table_name ADD co ...

Stored procedures are an important feature of database storage. Stored procedures were not supported by MySQL prior to version 5.0. Stored procedures can greatly improve the processing speed of the database and the flexibility of database programming.1. What is a stored procedure?Stored procedures are a collection of SQL statements that are de ...

Catalog Preface DDL DCL DML 1. Management database of DDL statements 1.1. Create database 1.2. Display database 1.3. Switch database 1.4. View the table information contained in the database 1.4.1. Switch to database to view table information 1.4.2. View the table information outside the library 1.5. Delete database 2. Manage users of ...