Course Introduction：In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.
2025-04-29 comment 0 776
Course Introduction：Database schema migration refers to the process of modifying the database structure without changing the data, which mainly includes adding or deleting tables, modifying column types or constraints, creating or deleting indexes, changing default values ??or nullable settings, etc. It is usually driven by application updates, for example, when new features need to store user preferences, new columns are added to the user table. Unlike data migrations that deal with large amounts of data movement, pattern migration focuses on structural changes. To perform mode migrations safely, version control should be used to track structure files, verify them in the test environment before the production environment, split the large migration into small steps, avoid multiple irrelevant changes in a single time, and note that changes to large tables may cause long-term table locking problems. You can use tools such as pt-online-schema-chan.
2025-07-06 comment 0 1002
Course Introduction：MySQL's ALTERTABLE statement is used to adjust the table structure and supports adding, modifying and deleting columns. 1. Use ADDCOLUMN to add a new column, and you can specify the location; 2. Use MODIFYCOLUMN to modify the column, and you need to pay attention to data conversion and dependency objects; 3. Use DROPCOLUMN to delete the column, and the operation is irreversible and the dependency will be cleared; 4. Multiple operations can be performed at once, and it is recommended to check the structure through DESCRIBE or SHOWCREATETABLE. Verify it in the test environment before operating in the production environment.
2025-07-15 comment 0 976
Course Introduction：SqlParameter Parameters.Add vs. AddWithValue: Choosing the Best MethodWhen working with SQL commands, you may encounter the need to add...
2025-01-10 comment 0 674
Course Introduction：In Dave The Diver, there are some creatures that are not easy to catch. Or, catch alive that is. The spider crab is one of those very species, making it seem like the only way to bring these crustaceans back up to land is to viciously crack them up w
2025-01-10 comment 0 819
Course Elementary 13778
Course Introduction：Scala Tutorial Scala is a multi-paradigm programming language, designed to integrate various features of object-oriented programming and functional programming.
Course Elementary 82289
Course Introduction："CSS Online Manual" is the official CSS online reference manual. This CSS online development manual contains various CSS properties, definitions, usage methods, example operations, etc. It is an indispensable online query manual for WEB programming learners and developers! CSS: Cascading Style Sheets (English full name: Cascading Style Sheets) is an application used to express HTML (Standard Universal Markup Language).
Course Elementary 13147
Course Introduction：SVG is a markup language for vector graphics in HTML5. It maintains powerful drawing capabilities and at the same time has a very high-end interface to operate graphics by directly operating Dom nodes. This "SVG Tutorial" is intended to allow students to master the SVG language and some of its corresponding APIs, combined with the knowledge of 2D drawing, so that students can render and control complex graphics on the page.
Course Elementary 24594
Course Introduction：In the "AngularJS Chinese Reference Manual", AngularJS extends HTML with new attributes and expressions. AngularJS can build a single page application (SPAs: Single Page Applications). AngularJS is very easy to learn.
Course Elementary 27454
Course Introduction：Go is a new language, a concurrent, garbage-collected, fast-compiled language. It can compile a large Go program in a few seconds on a single computer. Go provides a model for software construction that makes dependency analysis easier and avoids most C-style include files and library headers. Go is a statically typed language, and its type system has no hierarchy. Therefore users do not need to spend time defining relationships between types, which feels more lightweight than typical object-oriented languages. Go is a completely garbage-collected language and provides basic support for concurrent execution and communication. By its design, Go is intended to provide a method for constructing system software on multi-core machines.
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