Error Handling in SQL Server – Best Methods Guide

For working on the SQL Server environments, a user must be aware of the technicalities of the database, and the ways for error handling in SQL Server. These errors can occur due to various reasons. With the help of this article, we will understand about these errors thoroughly and we will also find the best solutions for the errors in SQL Server environments.

Starting with briefly understanding what SQL error handling is. 

Error Handling in SQL Server – Overview

As we can simply understand by the term, Error Handling means to handle and manage the errors occurring in the SQL Server databases. Error handling majorly includes the methods and operations to resolve the issues during the execution of SQL Operations. It also involves mechanisms that can be used to deal with unexpected issues in the SQL Servers, like runtime errors, syntax errors or uncertain hardware failures. 

So before moving to the problem handling methods, we will first understand the possible errors that can occur and require SQL error handling.

Before we step into the errors and the ways to handle them, it’s time that we focus on what an error is and how is it structured. This way, understanding an error can be easy. Thus, it helps in fixing the errors as well.

The error says a lot about itself in the very first line. Let’s have a look at it to understand the handling process of errors.

MSG #, Level #, State #, Line #

Explanation:

MSG – As we know that SQL Server has 50,000 errors, so the first number in front of MSG, represents these errors from 1 to 49,999. If users generate custom errors, that starts from 50001. However, we will talk about the user-generated errors later.

LEVEL – Now, the level shows the severity of the error. From 0 to 10, all number shows warning signs. However, levels number 11 to 16 are a bit more severe. Although users can fix these errors with minor corrections in the syntax, etc. Now, 17 to 24 are the most severe errors like OS issues, lack of resources, database crashes, etc.

STATE – Third one, the state shows the specific condition of the error and more information about it. It basically pinpoints the exact cause due to which the error is arising.

LINE – Finally, the Line shows the line number of the query where the error occurred to help users find out where exactly the mistake or problem is.

Types of Errors in SQL Server

There are various types of errors that can occur in the SQL Server environment.

• Syntax Error: As the error name suggests, this error occurs due to the errors in syntax of the SQL commands. When these errors occur, they restrict the SQL query from being executed. 
• Semantic Error: These errors occur when the complete SQL command is written with correct syntax but is logically incorrect. They can often occur due to the use of incorrect or invalid data types. 
• Runtime Error: The runtime error occurs at the time of SQL command execution. They can be caused due to incorrect operations in the SQL command. 
• Connection and Integration Errors: These errors occur when the SQL Server is unable to or fails to establish a connection with the other server or database. Similarly when a user uses incorrect configuration for the SQL Server, an error can occur.  Furthermore, some errors may also occur due to the problems with application integration as they may restrict the applications from fetching the data from SQL Server. 
• Logical Errors: There are some errors that are triggered due to incorrect query or logics performed by the users. The logical errors are majorly user-based errors and can be solved using proper error handling in SQL Server
• Data Errors: These errors occur due to data related issues in the SQL Server. These issues can be incorrect data types or invalid data formats being used in the SQL Servers. 
• Security Related Errors: Insufficient permissions, incorrect credentials or misconfigurations in the SQL Server are also a major reason for the errors to occur in the SQL Server.
• Backup & Restore Related Errors: When the SQL Server has backup issues or restoring issues, these can result in restricting the users from performing their daily operations in the SQL Server.

Why is Error Handling Necessary?

If we talk about the mentioned SQL errors, these errors often prevent and completely restrict the users from carrying out operations in SQL Server. So in these situations, the mechanisms involved in the error handling in SQL Server help to understand and resolve these errors.

Additionally, there are a few other benefits of the SQL error handling. Let’s take a look at all the benefits of error handling.

• For Data Integrity: The operations performed in the SQL Server databases are usually insertions, deletions, updates, and other modification commands. If proper error handling is not done, any error during these operations can hugely impact the database. 
• For Better User Experience: For database administrators and users who are working in the SQL Server environments, coming across SQL Errors can be puzzling. With proper error handling in SQL Server ways, the users can get a clear idea about the errors and can resolve them more accurately.
• For Reducing Downtime: Sometimes, when the SQL Server error occurs, the whole database or the system may face possible downtime, or crash. With error handling, these errors can be resolved much easily without impacting the complete system. 
• For System Maintenance: Error handling in SQL Server makes the maintenance of the database or systems easier for the database administrators. 
• For Better Security: Even for better security of the data present in the SQL Server database, SQL error handling plays an important role. 

How Error Handling Deals With These SQL Errors?

When the SQL Server encounters any error, be it logical, runtime, or any other error, the major requirement becomes to find the exact cause of that error. Error handling methods help the users to understand these errors and resolve them more efficiently. 

But, even for SQL error handling, there are certain requirements to be met for better results. These requirements are as follows:

Detection of the SQL Error

There are a few tools for error handling in SQL Server that can help the users detect the SQL errors. Detection of the accurate reason for the error is required to resolve the error completely. 

Better Management of Transactions

The transactions in the SQL Server can be described as all the operations that have to be  performed in the database. So it becomes important to manage these transactions properly. This management ensures that either all transactions take place at once or no transaction takes place at all. 

Thorough Monitoring

Monitoring errors and recording them with complete details can help the users and developers to understand the errors and resolve them accordingly. 

Secure Recovery

It is important to ensure that the SQL Server can easily recover after the error occurs and doesn’t result in locked databases or  corrupted data.

All these factors are required for efficient error handling in SQL Server. Additionally, there are certain ways and tools offered by the SQL Server itself that can help to figure out the errors and help the users to resolve them. 

Let’s now move to the SQL error handling methods offered by the SQL Server and understand how they work.

Also Read: What is SQL Server Index Optimization? – Complete Guide

Error Handling Methods By SQL Server 

1. The TRY and CATCH Method

While running SQL commands, you might encounter various errors. These errors can occur due to incorrect or invalid commands. The TRY and CATCH block majorly helps you to find and resolve these kinds of errors.  With using the TRY and CATCH block you can execute the SQL commands in a more efficient and error-free way. 

Let’s now take a look at how this method for error handling in SQL SERVER works.

• When you have to execute any SQL command, all you have to do is to add the TRY block inside the code. Even if the code is completely error free, use the TRY block as there is an error in the command. If the code is completely error free, the code will not even consider the CATCH block. 
• The CATCH block in this method primarily acts as a safety net. If there are any errors in SQL code, the SQL Server will move directly to the CATCH block. In the CATCH block, you can add a code for error handling in SQL Server or any other message as per your needs.  

Here is the SYNTAX on how to use the TRY and CATCH Block.

BEGIN TRY
– Code for execution
END TRY

BEGIN CATCH
– Code in case any error occur
END CATCH

2. Recording Detailed SQL Error in LOG Table

While working in the SQL Server database, keeping records and details of the error occurred can help the users and developers understand how and why the error occurred. Additionally, the developers can easily track the error and use appropriate methods for error handling in SQL Server. 

In the Log Table, the details usually mentioned are:

SQL Error Message: The message that is displayed when the error occurs. Mostly specifies the reasons due to which the error occurred. 

SQL Error Code: The code that is assigned to the specific SQL error that occurred. Helps the developers and users understand a little deeper about the SQL error.

Date And Time: The date and time when the error occurred. This helps the user and the developer to keep a track of the frequency of the SQL Error occurrence. 

3. RAISERROR and THROW Method  

During command execution in SQL, when error occurs, and notify the users, this method comes in action. The RAISERROR and THROW, both the  tools are useful in these situations for efficient error handling in SQL Server. 

The syntax of the Raise & throw command line method is:

RAISERROR ( { msg_id | msg_str | @local_variable }       
{ ,severity ,state }
[ ,argument [ ,...n ] ] )
[ WITH option [ ,...n ] ]

Both RAISERROR and THROW commands are used to send error messages when an error occurs in the SQL Server. These tools are majorly used for the following purposes:

• For Alerting the Users
• To Record Error Logs
• To Control Flow of SQL Processes

All these methods for error handling in SQL can be used to smoothly execute the SQL commands in the SQL Server.

Difference Between Error Handling and Exception Handling

In SQL Server, some users often use error handling or exception handling interchangeably. However, they are not exactly the same. They have distinct meanings in the context of SQL as we are going to understand that.

SQL Server Error handling is a broader concept as it includes all elements of detecting, diagnosing, and responding to errors. Moreover, it includes both system-generated as well as user-generated errors with RAISE and THROW error syntax.

SQL Server Exception Handling is used when it comes to handling a specific error in a structured way with a defined code block. The try-and-catch method is generally used here by users and SQL administrators.

Differences – The major differences are in terms of scope(error being broader and the exception being a bit narrow), mechanism(raise Vs try and catch), focus(detecting/diagnosing/responding Vs handling), and purpose.

Conclusion

Database administrators who work in the SQL Server environment, know how much errors can affect the complete SQL command execution. So to prevent these errors from occurring, one can use proper error handling methods. With help of these SQL error handling methods, users can resolve errors and continue with their day to day tasks.

FAQs

Q-1. How do I check for errors in SQL Server?

Ans: The basic way to check for errors is by executing the DBCC CHECKDB command.

Q-2. What is SQL Profiler in SQL Server?

Ans: Well, an SQL profile is an interface or tool that helps users create or even manage traces and analyze or replay trace results in depth.

Q-3. How do I show errors in SQL?

Ans: It’s really simple. Just use the SHOW ERROR command to show the errors.