Database version control is implemented through migration scripts to ensure that structural changes are traceable and rollable. 1. Why is it necessary: database structure changes are difficult to roll back, which can easily lead to inconsistency in the environment. Version control can record the change history and support restoration; 2. How to implement: Use migration scripts executed in sequence, record them in the schema_migrations table, combined with tools such as ActiveRecord Migrations or golang-migrate; 3. Notes: The script should be idempotent and include rollback logic, distinguish structure and data changes, and use scripts to synchronize the test environment uniformly; 4. Other suggestions: Regular backup of DDL, CI/CD to automatically perform migration, and check structural consistency before going online.

Managing versioning of SQL databases sounds like a "should be done but always ignored" thing in the development process. Actually it is not complicated, but it is indeed prone to errors. Especially in the scenario where multiple people collaborate and frequently launch changes, the database structure without version control is like changing a light bulb in the dark, and accidentally breaking the short.

Let’s talk about how to do this right from a few key points.

Why does the database structure also require version control?

Changes to the database structure, such as adding fields, modifying indexes, disassemblying tables, and merging tables, are not as easy to "roll back" as code. Once an error occurs online, it is much more complicated to recover than the code. Moreover, the structural inconsistency between development, testing, pre-release and production environments is easy to lay mines.

The role of version control is to make every change traceable and playbackable. Just like Git to code, it lets you know "who changed what when" and safely restore it when needed.

How to establish version control for database structure?

A common practice is to use Migration Scripts to record every structural change. These scripts are executed in order and recorded in a table in the database, such as schema_migrations , which contains the version number and execution time.

For example:

• 001_create_users_table.sql
• 002_add_email_to_users.sql
• 003_create_orders_table.sql

Before each time, the system will check the current database version and then run those scripts that have not been executed. This ensures that the structure is consistent between the environments and can also conveniently back the version.

In terms of tools, you can select models based on the technology stack, such as:

• Rails has ActiveRecord Migrations
• Django has built-in migrations module
• Go can use golang-migrate
• Node.js can be used with TypeORM or db-migrate

Of course, you can also write a simple script to manage these changes yourself, as long as the logic is clear.

What details should be paid attention to in practice?

1. The script should be idempotent or repeatable
   Sometimes the script may fail to execute or need to be executed repeatedly. For example, it is best to determine whether the field exists before adding a field to avoid repeated errors.

    ALTER TABLE users ADD COLUMN IF NOT EXISTS email VARCHAR(255);

2. Don't skip the rollback script
   Once there is a problem online, you have to be able to roll back quickly. Therefore, it is best to write a "reverse" script at the same time for each change, such as deleting fields, restoring indexes, etc.

3. Structural changes and data migration should be distinguished
   Some changes not only change the structure, but also update the data. This type of operation should be especially careful, and it is best to perform during off-peak periods to avoid table locking or affecting performance.

4. The test environment also needs to use migration scripts to synchronize the structure
   Do not manually modify the test library structure, as it will easily be inconsistent with the production environment. Only by using migration scripts to ensure that the test is effective.

What else should you pay attention to in addition to version control?

In addition to version control of structural changes, you can also improve the reliability of database management by following practices:

• Regularly backup database structures (such as exporting DDL)
• Use CI/CD to automatically execute migration scripts to avoid human misses
• Check the structure change before going online (such as whether the field type is correct and whether the index is missing)

These details add up to make database changes more controllable and easier to troubleshoot problems.

Basically that's it. Database version control is not complicated, but is easily overlooked. As long as you record each change clearly and cooperate with appropriate tools, many online accidents can be avoided.

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