When designing databases, some guidelines need to be followed in case we want to build an effective and useful database system. This article elaborates on best practices when it comes to SQL Server database design.
Database Design Basics
Implementation of SQL database structure is a complex process. The process requires the developer to have good knowledge of database design. It consists of many smaller parts that could be observed separately. Each part of it could be represented as an objective within a SQL database structure implementation guideline.
In case we want to learn database design best practices, we should bear in our mind the following objectives:
- Data Integrity
Every database should hold only data that is relevant to a particular organization. This means that, prior to designing a database, we need to have a series of meetings with our business users. These meetings will help us get a clear insight into the business requirements. We should ask about every single detail related to data that our users use:
- Will our database be used only for data collection, or will it be used for data analysis as well?
- What kind of data will be stored in a database?
- What kind of operations will be done over the particular datasets?
- How frequently particular datasets are being used, and in which way?
- Which users use which datasets?
After we understand the business requirements and the business process that our database should support, we will be able to organize the data. This data organization should be done by using appropriate SQL data structures.
After we realize the business process and the data used within, the next step is to organize that data as efficient as possible. This efficiency is reflected in the following:
- Simplicity – the simple the database is, the easier it will be to use and maintain in the future.
- Generalization – we need to generalize as much of the database as possible due to the easy database maintenance. In regards to this, we need to take care of the following:
- Define naming convention on a database level: every object type needs to have a particular naming convention defined. It is much easier to deal with consistent database design, especially if many developers work on its implementation.
- Define rules
- Define the user-defined types and apply rules upon them
- Define sequences if needed
- Ensure Entity Integrity
- Define tables for particular datasets.
- Define the primary key for each table.
- Ensure Domain Integrity
- Define the data type correctly for each table column
- Apply rules and/or user-defined types on table columns in order to generalize the SQL table design as much as possible
- Apply constraints on table columns
- Ensure Referential Integrity
- Implement foreign keys on particular tables that are logically interconnected
- Ensure Transactional Integrity
- Implement ACID properties on each transaction performed within the database
- Ensure User-Defined Integrity
- Implement business rules that cannot be solved by using the primary key, foreign key, or any other constraint provided as built-in functionality. Such complex rules could be implemented by using either stored procedures, triggers, or a SQL query as identifiers of incorrect data and handling those data properly.
Flexibility is a crucial property of good database design. No matter how detailed we are at the beginning of the process of establishing the database, most of the time, business requirements change as time goes by. Those changes almost always reflect our SQL database design.
Therefore, it is a must to design a database in such a way that the adding of new tables and other database objects are easily done. This feature is largely related to the simplicity and generalizing the database objects during the schema design.
To be able to read data quickly is a default business requirement. Developers often neglect the performance at the beginning of the SQL database design process. It can lead to user dissatisfaction as data is increasing day by day. If we want to have a database that performs well, we need to be sure we implement the following:
- A well-designed schema with tables that are in 3rd normal form
- Creation of clustered and non-clustered indexes if and where needed
- Creation of transactions that run without locking and blocking
- Usage of partitioning if needed
Data security ensures that a particular dataset is accessible only to particular users that use the dataset. This should be a primary concern when creating a database system in order to avoid unwanted situations like changing or deleting data by unauthorized users. This is why we should define at the beginning of the SQL database design process which and in which ways some user uses particular dataset(s). After we define this, we should implement the following:
- Create server roles
- Create logins
- Assign server roles to the logins accordingly
- Grant/deny permissions to the data center on a login level
Users should be able to use data whenever they need it. Sometimes some situations could lead to data or data access loss. In regards to that, we as developers should provide mechanisms that will enable them the alternative ways to access the database. This includes the following:
- Ensure redundant hardware
- Implement a disaster recovery plan
- Implement procedures related to database backup and backup storage
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