Mastering SQL Database Comparison: A Guide to SQL Compare

The basic idea behind SQL Compare is to Compare SQL changes between the two SQL Server databases. It will produce a script that joins the destination database’s schema to the source database’s schema. This article examines all the ways that this can be useful in database development and deployment, including auto-creating deployment scripts, identifying database drift, and generating database scripts in version control.

SQL Compare: What Is It?

A GUI tool for comparing SQL Server databases is called SQL Compare. It will examine the structural variations in the source and target databases and display the variations in the SQL DDL code of each table and code module side by side. The tool will produce a deployment script, also known as a ‘1-way synchronization’ or ‘migration’ script, which will update the target database to match the source database’s structure after you Compare SQL changes. The script will attempt to preserve current data whenever feasible and will issue a warning if it doesn’t. You have control over how SQL Compare performs this comparison and which items it ignores by utilizing its options and filters.

For Windows and Linux, SQL Compare has a command line interface that can be used to Compare SQL changes and might be covered by a separate, automation-based license. It enables you to run the deployments and comparisons as a scripted procedure. SQL Compare can produce an HTML or Excel file as a report when it is used from the command line or a script.

The comparison engine of SQL Compare is integrated into SQL Change Automation and SQL Source Control as well.

What is the process by which SQL Compare operates?

Schemas from databases—more precisely, from two distinct iterations of the same SQL Server database—can be compared using SQL Compare. SQL Compare may operate with any representation of a database to Compare SQL changes and create a ‘model’ of the structure of that database, therefore the source and target don’t necessarily have to be “live” SQL Server databases. It may parse a scripts folder, for instance, which has a set of DLL scripts for each database object, into a single build script or even a database model. In the same vein, it can function with a SQL Change Automaton project file, an SQL Source control project, or a SQL Compare Snapshot.

Upon comparison, SQL Compare will produce a list of database objects that are unique to either the source or the target, or that are present in both but differ from one another. It may automatically build the deployment (also known as ‘schema migration’) script to Compare SQL changes, which, if run, will change the target’s metadata to match the source’s, and it will show the differences in each object’s metadata in script form.

If the target is a database, the script will update each object that is in both so that its definition matches that in the source, create any objects that exist only in the source, and drop any objects that exist only in the target. Similar to this, files are added, removed, or changed to reflect the source database if the target is an already existing DDL code directory. SQL Compare will alert you to any potential problems in each scenario, even if it is unable to save the current data. Before deploying the generated migration script to the target, you can review it and make any necessary changes.

SQL Compare offers different options to govern how the comparison and subsequent scripting are carried out, as well as filters to control which items are included in the comparison.

The auto-generated schema migration script for SQL Compare operates inside a transaction and will automatically roll back if a problem occurs. If some items, such as full-text indexes, can’t be deployed in a transaction, you’ll be notified and they’ll be deployed individually.

Conclusion

SQL Compare offers a robust solution for comparing SQL changes and automating schema synchronization. Examining structural differences and generating deployment scripts, simplifies database management. Its integration with SQL Change Automation and SQL Source Control further enhances efficiency, making it an essential tool for developers.