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Single responsibility Single function Single function is the most basic requirement of SRP, that is to say, the function and responsibility of your class should be single, so that cohesion is high. For example, the following parameter class is used to query website Buyer information, according to SRP, it should be placed in the query Field. @Da ...

Mysql Misoperation Quick Restore Data background In the daily work process, ECM has a large number of scenarios of manual direct operation of the database to modify data, which is difficult to achieve absolute certainty. When there is no backup and a large amount of data is updated or deleted by mi ...

1. MySQL multi-table query 1.1 Foreign Key Constraints In order to eliminate the Cartesian product in multi-table queries, MySQL can use foreign key Association queries when building tables and performing key queries between multiple tables. Foreign key: Refer to the value of one column in Table 1 (sub) and another column in Table 2 (main), ...

Problem Description R&D colleagues feedback that an application is slow to execute, corresponding to SQL: UPDATE bs_serial_trac SET SERIAL_IS_LOCK = 0, LOCK_VALUE = '', UPDATE_USER = 'transSys' WHERE GOODS_NO = '4418095740626' AND ( PARENT_CODE = 'F9G7S19722001835' OR SERIAL = 'F9G7S19722001835' ); The index on table bs_s ...

Splicing of SQL Statements In the previous configuration, whether basic additions, deletions, modifications, or association nesting, set nested queries, the use of SQL statements are very basic, data operations between tables. Turn back to the code you wrote in your freshman year and splice the SQL ...

1. SQL execution process 1.1 Internal execution of SQL statements MySQL is divided into Server layer and Storage Engine layer. Server layer includes connectors, analyzers, optimizers, executors and so on, while storage engine layer is responsible for data storage and reading.When SQL is executed, connections are established and privileges are o ...

Next, we begin to analyze the security.php source code, which is an important file of event in the dashboard sub-module. // Referencing files, initializing function libraries require_once 'av_init.php'; require_once 'sensor_filter.php'; require_once '../widget_common.php'; require_once 'common.php'; // Check if you have permission to ac ...

Structured Query Language (SQL) is a special purpose programming language. It is a database query and programming language for accessing data, querying, updating and managing relational database systems. Add a self-increasing ID field ALTER TABLE tblname ADD COLUMN csmid COUNTER (0, 1) access creates a table with self-increasing fields CREATE T ...

Links to the original text: https://wallimn.iteye.com/blog/1199561 Checkpoint classification 1. System checkpoints (recorded in control files) SQL> select checkpoint_change# from v$database; CHECKPOINT_CHANGE# ------------------ ...

Building tables CREATE TABLE `user` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(10) DEFAULT NULL, `sex` tinyint(1) DEFAULT NULL, `age` tinyint(2) DEFAULT NULL, PRIMARY KEY (`id`), KEY `Index_user` (`name`,`age`) USING BTREE ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4; Testing sql First mysql> exp ...