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When working with SQL servers and databases, managing schema changes is absolutely essential. It can get quite cumbersome and confusing, particularly in large projects or when several developers are involved. To keep everything in control, we use database versioning techniques. In this post, we will explore how you can manage schema changes using SQL Server.
What is Database Versioning?
Database versioning is the practice of tracking and controlling changes to a database’s schema. Schema in a database refers to the organisation and structure of data. Versioning helps to prevent conflicts between different versions of the same database, particularly in a team environment.
Using SQL Server for Schema Changes
SQL Server offers a number of methods to track and manage schema changes. Here we are going to illustrate the procedure with an example using a simple table.
Creating the Initial Table
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CREATE TABLE Employees ( EmployeeID int, FirstName varchar(255), LastName varchar(255), Department varchar (255), Salary int, ); |
This basic Employees table contains an ID, the employee’s first and last name, their department, and their salary.
Adding a Version Column
To implement versioning, we are going to add another column to our table – the Version column. This will be an integer type that will be incremented with each change to the schema. The latest version of the table schema will have the highest version number.
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ALTER TABLE Employees ADD Version int; |
Incrementing the Version on Schema Change
The next step is to create a procedure which will increment the version number each time the schema changes.
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CREATE PROCEDURE IncrementVersion AS UPDATE Employees SET Version = Version + 1; GO |
Now, whenever a schema change occurs, the Version column will be incremented by one.
Adding New Columns
Let’s say we want to add a new column for Employee’s age, we will use ALTER command which will not only update the schema but also increment the version automatically.
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ALTER TABLE Employees ADD Age int; EXEC IncrementVersion; |
Final Thoughts
SQL Server Database versioning is a pro-active method for managing schema changes in your projects. Tracking the evolution of your schema can save lots of headaches when dealing with problematic migrations or database discrepancies. Of course, the process can be much more detailed on complex projects, but understanding the basics gives you a good ground to start on.
Remember, the aim is to keep the database environment as stable as possible, and SQL Server provides us with robust tools to achieve this.