When do sql triggers fire

And worse it will not fail with an error, it will simply not affect all the rows you want affected by whatever the trigger does.

Do not fix this through a loop or a cursor in a trigger, change to set-based logic. A cursor in a trigger can bring your entire app to a screeching halt while a transaction of , records processes and locks up the table for hours. Bulk inserts by pass triggers unless you specify to use them. Be aware of this because if you let them by pass the trigger you will need code to make sure whatever happens in the trigger also happens after the bulk insert.

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Viewed 29k times. Pretty general question regarding triggers in SQL server In what situations are table triggers fired and what situations aren't they? That is an absolute beast in terms of complexity. While it accepts scalar parameters to determine a calculated price, the operations it performs are vast and even include additional reads to Warehouse.

StockItemStockGroups , Warehouse. StockItems , and Sales. If this is a critical calculation that is used against single rows of data often, then encapsulating it in a function is an easy way to get the needed calculation without introducing the added complexity of triggers.

Use caution with functions and be sure to test with large data sets. A simple scalar function will generally scale well with larger data, but more complex functions can perform poorly.

A stored procedure could also be used, but the function might provide the added benefit of inlining the operation, allowing the calculation to occur as part of a write operation.

An added benefit of this approach is that the code resides in one place and can be altered whenever needed in one place. Similarly, places that utilize the function can be adjusted to stop using it, or change how they use it. All of this can be accomplished independently of triggers, ensuring that code remains relatively easy to document and maintain, even if the logic underneath it is as complex as in the function presented above.

When data is modified in a table from an application, it can also perform additional data manipulation or validation prior to writing the data.

This is generally inexpensive, performs well, and helps reduce the negative impact of runaway triggers on a database.

The common rationale for putting code into triggers instead is that it avoids the need to modify code, push builds, and otherwise incur the time and risk of making application changes. This runs directly counter to any risk related to making changes within the database.

Often this is a discussion between application developers and database developers as to who will be responsible for new code. This is a rough guideline but helps in measuring maintainability and risk after code is added either to an application or a trigger. Computed columns are exceptionally useful ways to maintain metrics in a table that stay up-to-date, even as other columns change.

A computed column can include a wide variety of arithmetic operations and functions. They can be included in indexes, and if deterministic, then they can be included in unique constraints and even primary keys. Computed columns are automatically maintained by SQL Server when any underlying values change and cannot be inserted or updated. Note that each computed column is ultimately determined by the values of other columns in the table.

This is an excellent alternative to using triggers to maintain special column values. Computed columns are efficient, automatic, and require no maintenance. They simply work and allow even complex calculations to be integrated directly into a table with no additional code required in the application or in SQL Server. Triggers are sometimes used for managing queues and messaging as a way to ensure that DML directly results in tasks to be processed asynchronously elsewhere in the future.

While this works, it also ties together the source transactional process to a destination messaging process. This can be expensive, complex, and hard to maintain. Service Broker is built to manage sending messages between queues and does so efficiently. It can be used for simple use-cases, such as queuing tasks to process or logging processes to execute at a future time. It can also be used to divide processing workloads between servers, allowing expensive ETL or other costly processes to be offloaded away from a critical production system and onto another system dedicated to those purposes.

Service Broker is a mature SQL Server feature, but one that includes quite a bit of new syntax to learn and use, therefore this article is not an ideal place to walk through its use. It will usually be the right tool for the job and avoids the need to manually maintain queue tables and queue-management processes. Databases are not designed to be good queues, so implementing Service Broker or a 3 rd party utility designed for this purpose will provide an easier-to-maintain solution that performs better.

Triggers are a useful feature in SQL Server, but like all tools, one that can be misused or overused. If a trigger is being used to write brief transaction data to a log table, it is likely a good use of a trigger.

If the trigger is being used to enforce a dozen complex business rules, then odds are it is worth reconsidering the best way to handle that sort of validation. With many tools available as viable alternatives to triggers, such as check constraints, computed columns, and temporal tables, there is no shortage of ways to solve a problem.

Success in database architecture is choosing the correct tool for the job, knowing that the time spent on that decision will save far more time and resources in the future had a poor decision been made. If you like this article, you might also like Triggers: Threat or Menace? SQL Monitor helps you keep track of your SQL Server performance, and if something does go wrong it gives you the answers to find and fix problems fast.

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In his free time, Ed enjoys video games, traveling, cooking exceptionally spicy foods, and hanging out with his amazing wife and sons. View all articles by Edward Pollack.

Federal Healthcare Managed Service Providers. What are triggers? What do triggers look like? To solve this problem via triggers, the following steps could be taken: 1.

ON Sales. OrderID , Deleted. WHEN Inserted. WHEN Deleted. FROM Inserted. ON Inserted. OrderID ;. FROM sales. EXEC dbo. Design your applications not to rely on the firing order of multiple triggers of the same type. Data Access for Triggers When a trigger is fired, the tables referenced in the trigger action might be currently undergoing changes by SQL statements contained in other users' transactions. In particular, if an uncommitted transaction has modified values that a trigger being fired either needs to read query or write update , the SQL statements in the body of the trigger being fired use the following guidelines: Queries see the current read-consistent snapshot of referenced tables and any data changed within the same transaction.

Updates wait for existing data locks before proceeding. The following examples illustrate these points. Therefore, the second user waits until the commit or rollback point of the first user's transaction.

Storage for Triggers For release 7. Execution of Triggers Oracle internally executes a trigger using the same steps used for procedure execution. Other than this, triggers are validated and executed the same way as stored procedures. Newsletter Topics Select minimum 1 topic. Table1 Select col1, col2, col2 From dbo. How can I make it fire for all the rows being inserted? Standard answer applies: it depends Cursors do have overhead.

Anonymous Posted May 6, 0 Comments. Why do you need a trigger at all? Why not the insert stored proc take care of everything? Hi Kalman, we dont insert large volumes of data. If you are are only inserting 10 records, you only have to worry about the indexes. Register or Login. Welcome back!