Answer.

Stored procedures are programmable blocks that are explicitly called and can accept parameters, execute complex business logic, work with transactions, and return data sets or output parameters.

Triggers are special objects that "automatically" fire on data modification events (INSERT, UPDATE, DELETE), ensuring transparent execution of specified logic during certain actions on a table.

When to use procedures

• Large volumes of data need processing.
• Explicit transaction control is required.
• A result or multiple data sets need to be returned.

When to use triggers

• Implicit checks or updates need to be guaranteed on any data change (for example, auditing).
• Comprehensive integrity checks need to be implemented.

Code example

Stored Procedure:

CREATE PROCEDURE UpdateProductPrice
  @ProductID int, @NewPrice money
AS
BEGIN
  UPDATE Products SET Price = @NewPrice WHERE ProductID = @ProductID;
END

Trigger:

CREATE TRIGGER trg_ProductsPriceChange
ON Products
AFTER UPDATE
AS
BEGIN
  INSERT INTO PriceAuditLog(ProductID, OldPrice, NewPrice, ChangeDate)
  SELECT i.ProductID, d.Price, i.Price, GETDATE()
  FROM inserted i JOIN deleted d ON i.ProductID = d.ProductID
  WHERE i.Price <> d.Price
END

Trick question.

Q: Can the order of execution of multiple AFTER triggers on the same table in SQL Server be determined by standard means?

A: No, the SQL standard does not guarantee the order of execution of AFTER triggers of the same type on the same table. If the order is important, they should be combined into one.

Examples of real errors due to ignorance of the topic nuances.

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Story

In a CRM solution for supporting change history functionality, triggers were used. Due to the high load from mass updates, records in the log were entered with a delay and blocked "live" operations, causing temporary unavailability of the service.

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Story

A developer created logic for data validation not in a procedure but in a trigger, expecting that users would see the changes instantly. Forgetting that the trigger is "transparent," they faced the situation where the business logic became non-obvious (like "magic") and was difficult to debug.

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Story

Important: Often, a procedure is called within a trigger, or a trigger from a procedure, leading to recursion and exceeding the nesting limit—for example, automatic insertion leads to the trigger being fired again through the related procedure.