Is there a version control system for database structure changes?
I often run into the following problem.
I work on some changes to a project that require new tables or columns in the database. I make the database modifications and continue my work. Usually, I remember to write down the changes so that they can be replicated on the live system. However, I don't always remember what I've changed and I don't always remember to write it down.
So, I make a push to the live system and get a big, obvious error that there is no NewColumnX, ugh.
Regardless of the fact that this may not be the best practice for this situation, is there a version control system for databases? I don't care about the specific database technology. I just want to know if one exists. If it happens to work with MS SQL Server, then great.
Solution 1:
In Ruby on Rails, there's a concept of a migration -- a quick script to change the database.
You generate a migration file, which has rules to increase the db version (such as adding a column) and rules to downgrade the version (such as removing a column). Each migration is numbered, and a table keeps track of your current db version.
To migrate up, you run a command called "db:migrate" which looks at your version and applies the needed scripts. You can migrate down in a similar way.
The migration scripts themselves are kept in a version control system -- whenever you change the database you check in a new script, and any developer can apply it to bring their local db to the latest version.
Solution 2:
I'm a bit old-school, in that I use source files for creating the database. There are actually 2 files - project-database.sql and project-updates.sql - the first for the schema and persistant data, and the second for modifications. Of course, both are under source control.
When the database changes, I first update the main schema in project-database.sql, then copy the relevant info to the project-updates.sql, for instance ALTER TABLE statements. I can then apply the updates to the development database, test, iterate until done well. Then, check in files, test again, and apply to production.
Also, I usually have a table in the db - Config - such as:
SQL
CREATE TABLE Config
(
cfg_tag VARCHAR(50),
cfg_value VARCHAR(100)
);
INSERT INTO Config(cfg_tag, cfg_value) VALUES
( 'db_version', '$Revision: $'),
( 'db_revision', '$Revision: $');
Then, I add the following to the update section:
UPDATE Config SET cfg_value='$Revision: $' WHERE cfg_tag='db_revision';
The db_version only gets changed when the database is recreated, and the db_revision gives me an indication how far the db is off the baseline.
I could keep the updates in their own separate files, but I chose to mash them all together and use cut&paste to extract relevant sections. A bit more housekeeping is in order, i.e., remove ':' from $Revision 1.1 $ to freeze them.
Solution 3:
MyBatis (formerly iBatis) has a schema migration, tool for use on the command line. It is written in java though can be used with any project.
To achieve a good database change management practice, we need to identify a few key goals. Thus, the MyBatis Schema Migration System (or MyBatis Migrations for short) seeks to:
- Work with any database, new or existing
- Leverage the source control system (e.g. Subversion)
- Enable concurrent developers or teams to work independently
- Allow conflicts very visible and easily manageable
- Allow for forward and backward migration (evolve, devolve respectively)
- Make the current status of the database easily accessible and comprehensible
- Enable migrations despite access privileges or bureaucracy
- Work with any methodology
- Encourages good, consistent practices
Solution 4:
Redgate has a product called SQL Source Control. It integrates with TFS, SVN, SourceGear Vault, Vault Pro, Mercurial, Perforce, and Git.
Solution 5:
I highly recommend SQL delta. I just use it to generate the diff scripts when i'm done coding my feature and check those scripts into my source control tool (Mercurial :))
They have both an SQL server & Oracle version.