Structured Query Language (SQL) - Cultural View of Technology

Commit (data management) 21
Commit (data management)
In the context of computer science and data management, commit refers to the idea of making a set of tentative
changes permanent. A popular usage is at the end of a transaction. A commit is the act of committing.
Data management
A COMMIT statement in SQL ends a transaction within a relational database management system (RDBMS) and
makes all changes visible to other users. The general format is to issue a BEGIN WORK statement, one or more
SQL statements, and then the COMMIT statement. Alternatively, a ROLLBACK statement can be issued, which
undoes all the work performed since BEGIN WORK was issued. A COMMIT statement will also release any
existing savepoints that may be in use.
In terms of transactions, the opposite of commit is to discard the tentative changes of a transaction, a rollback.
Revision control
Commits are also done for revision control systems for source code such as Subversion or Concurrent Versions
System. A commit in the context of these version control systems refers to submitting the latest changes of the
source code to the repository, and making these changes part of the head revision of the repository. Thus, when other
users do an UPDATE or a checkout from the repository, they will receive the latest committed version, unless they
specify they wish to retrieve a previous version of the source code in the repository. Version control systems also
have similar functionality to SQL databases in that they allow rolling back to previous versions easily. In this
context, a commit with version control systems is not as dangerous as it allows easy rollback, even after the commit
has been done.
See also
• Atomic commit
• Two-phase commit protocol
• Three-phase commit protocol