Being a SQL Server Database Administrator (DBA) is a challenging role that requires a deep understanding of SQL Server concepts and best practices. However, even experienced DBAs can make mistakes that can impact the performance and stability of the database. In this article, we will discuss some common mistakes to avoid as a SQL Server DBA.

1. Comparing NULL Values

One common mistake is assuming that two NULL values are equal to each other. SQL Server does not consider NULL values as equal, so it’s important to use the appropriate comparison operators when dealing with NULL values.

2. Renaming Triggers

Renaming triggers without considering the impact can lead to unexpected behavior. It’s important to thoroughly test the renamed trigger to ensure it continues to function as expected.

3. Understanding Index Scan vs Table Scan

Confusing index scans with table scans can lead to inefficient query performance. It’s essential to understand the differences between these two operations and use the appropriate one based on the query and table structure.

4. Reinstalling SQL Server for Forgotten Password

Reinstalling SQL Server should not be the solution for a forgotten SA login password. There are alternative methods to recover or reset the password without reinstalling the entire server.

5. Using Model Database for Testing

The model database should not be used for testing scripts. It is a template database used to create new databases. Instead, create a separate database specifically for testing purposes.

6. Compiled Stored Procedures

Believing that a compiled stored procedure is automatically production-ready is a misconception. While compilation can improve performance, it does not guarantee the correctness or efficiency of the code. Thorough testing is still necessary.

7. Prefixing Stored Procedures with ‘sp_’

Prefixing stored procedures with ‘sp_’ is not necessary and can lead to confusion. The ‘sp_’ prefix is reserved for system stored procedures in SQL Server. It’s best to use a meaningful and descriptive naming convention for stored procedures.

8. Moving Million Records with Stored Procedures

Using a stored procedure to move a large number of records across databases can be inefficient and resource-intensive. Consider using other methods, such as bulk insert or SSIS, for better performance.

9. Indexing All Fields

Indexing all fields in a database may seem like a good idea for performance improvement, but it can actually have a negative impact. It’s important to carefully analyze and select the appropriate fields for indexing based on query patterns and data usage.

10. Applying Relationships with ‘Enforce Relationship’ Unchecked

Unchecking the ‘Enforce Relationship’ checkbox when adding a foreign key constraint is not recommended. It can lead to data integrity issues and inconsistent relationships. Always ensure that relationships are enforced to maintain data integrity.

11. Using SELECT * Instead of Specifying Columns

Using SELECT * to retrieve all columns from a table may seem convenient, but it can lead to unnecessary data retrieval and potential performance issues. It’s best to explicitly specify the required columns in the SELECT statement.

12. Rules vs Constraints

Believing that rules are better than constraints and attempting to convert all constraints to rules is not recommended. Constraints provide more flexibility and control over data integrity compared to rules.

13. Adding a New Column in Four Steps

Adding a new column in four steps, including creating a new table and copying data, can be a time-consuming and error-prone process. Instead, use the ALTER TABLE statement to add a new column directly.

14. Auto-Creation of Clustered Index with Primary Key

There is no bug in SQL Server that automatically creates a clustered index every time a primary key is created on a table. The creation of a clustered index is a separate step and should be done based on the specific requirements of the table.

Conclusion

As a SQL Server DBA, it’s important to be aware of these common mistakes and avoid them to ensure the smooth operation of the database. By understanding SQL Server concepts and best practices, you can optimize performance, maintain data integrity, and avoid unnecessary complications.