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With the emergence of big data and a large number of data systems, data loading has become more and more important. Many jobs even need ETL skills. However, today, data loading is no longer a simple ETL, but also ELT, and even does not need data mobile computing. This paper first focuses on the traditi ...

Interaction between front end and back end and database operation 1. Query operation In mapper, select tag is used to complete the query operation. The sql statement used is select *from data table name. Or change * to the specific field value to be accepted, such as id, username and password. Then ...

Author: kay is good at Oracle, mysql, PostgresSQL and other database fields. He is good at Oracle, MySQL performance optimization, database architecture design, database fault repair, data migration and recovery. He is keen on studying MySQL database kernel source code and sharing technical articles. He has Oracle OCP certification and works i ...

Article directory I. concept 1, understand 2. Application scenario 2, Database operations 1. Create database 2. Data operation (add, delete, modify and query) 2.1 add statement Method 1: Method 2: 2.2 delete statement 2.3 UPDATE statement 2.4 query statement 3. Import of mobile database file ...

Preface After a noisy day, problems such as too many redirects to visit the Druid login interface and no login interface can be seen are finally solved. Let's go through how to integrate Druid on native JDBC. 1, Create a new project integrating JDBC data sources [1] Introduction of starter [2] Confi ...

The difference between PDO and Mysqli For PHP 5 and above, the following methods are recommended to connect to MySQL: MySQLi extension ("i" means improved) PDO (PHP Data Objects) PDO is used in 12 different databases, MySQL is only for MySQL database. Both support preprocessing statements to ...

introduce Druid is first a database connection pool. Druid is the best database connection pool at present, surpassing other database connection pools in function, performance and scalability. Druid has deployed more than 600 applications in Alibaba, which has passed the severe test of large-scale deployment of production environment for more t ...

Introduction to MySQL database Learning notes (2) Simple query SELECT column_name1, column_name2 FROM table_name; #select name,phone from person; SELECT * FROM table_name; #select * from person; * indicates all contents in the query table Conditional query where clause is required for condition q ...

Flask Flask is a lightweight WSGI Web application framework. It is designed to make it easy to get started and has the ability to scale to complex applications. It was originally a simple wrapper around Werkzeug and Jinja and has become one of the most popular Python Web application frameworks. from fl ...

Existence reason When we query in the database, we write fixed SQL, that is to say, we have to write a SQL for each query. But in the program, it is obvious that if there are too many fields in a table, we can query and update according to the combination of any fields. The amount of code is particul ...