Controlling Trigger Execution: Disabling, Conditional Logic, and Transactions in T-SQL

This is the most straightforward method:

DISABLE TRIGGER [SchemaName].[TriggerName];

Example:

DISABLE TRIGGER dbo.MyUpdateTrigger;

This statement disables the trigger named MyUpdateTrigger in the dbo schema. However, it permanently disables the trigger, not just temporarily.

Conditional Logic within the Trigger:

You can modify the trigger's logic to check for a specific condition and only execute its code if the condition is not met. This essentially "skips" the trigger behavior under certain circumstances.

CREATE TRIGGER MyUpdateTrigger
ON MyTable
AFTER UPDATE
AS
BEGIN
  DECLARE @disable INT;

  SELECT @disable = ISNULL([DisableTriggerFlag], 0) FROM MyFlags;

  IF @disable = 0
  BEGIN
    -- Trigger logic here
    UPDATE MyOtherTable
    SET ...;
  END;
END;

In this example, the trigger first checks a flag (DisableTriggerFlag) in another table. If the flag is set to 0 (indicating not disabled), the trigger executes its update logic on another table (MyOtherTable). Otherwise, it does nothing.

Using Transactional Control:

You can wrap your data manipulation statements (e.g., INSERT, UPDATE, DELETE) within a transaction and disable the trigger temporarily within that transaction:

BEGIN TRANSACTION;

DISABLE TRIGGER MyTableTrigger;

-- Your data manipulation statements here

ENABLE TRIGGER MyTableTrigger;

COMMIT TRANSACTION;

This approach disables the trigger only for the duration of the transaction, ensuring it fires again for subsequent operations.

Considerations:

• Disabling triggers permanently alters their state. Ensure you understand the implications before using DISABLE TRIGGER.
• Conditional logic within triggers adds complexity. Carefully test and maintain such triggers to avoid unintended behavior.
• Transactional control can introduce overhead. Use it judiciously only when necessary.