Executing a stored procedure within a stored procedure

Ensuring synchronization

T-SQL does not necessarily support asynchronous process runs. However, due to the synchronous nature of the EXEC command, the parent stored procedure (ParentProcedure) will patiently wait in the queue for the child stored procedure (NestedProcedure) to finish its task.

-- Inside ParentProcedure
-- "Don't rush, NestedProcedure. Safety first!"
EXEC NestedProcedure @Value1, @Value2;
-- Here, ParentProcedure waits for NestedProcedure to finish
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This helps in maintaining process integrity and ensures operations swiftly line up in the desired sequence. It's like gracefully avoiding traffic during the rush hour!

Manoeuvring parameters and results

Transfer of parameters

When calling NestedProcedure from ParentProcedure, ensure parameter matching to avoid any SQL tantrums:

-- ParentProcedure definition
-- "Passing the baton in a relay race!"
CREATE PROCEDURE ParentProcedure @ParentParam1 INT, @ParentParam2 INT AS
BEGIN
  ...
  EXEC NestedProcedure @ChildParam1 = @ParentParam1, @ChildParam2 = @ParentParam2;
  ...
END;
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Grabbing output

To snag the output of a nested stored procedure:

DECLARE @OutputValue INT;

-- "Catch the output!"
EXEC NestedProcedure @InputValue, @OutputValue OUTPUT;

SELECT @OutputValue AS 'OutputValue';
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Makes you feel like a magician pulling rabbits (outputs, in this case) out of a hat!

Climbing up the common usage and caution ladder

Keeping transactions in check

While nesting stored procedures, maintaining transaction control becomes like walking a tightrope. Here's a way to stay balanced:

BEGIN TRANSACTION;

BEGIN TRY
  -- "We don't make mistakes, just happy little accidents."
  EXEC NestedProcedure;
  COMMIT TRANSACTION;
END TRY
BEGIN CATCH
  ROLLBACK TRANSACTION;
  PRINT 'Oopsie daisy! An error slipped through.';
  -- Error handling goes here, like cleaning up after a drop of ice cream. 🍦
END CATCH;
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Error Propagation

Errors should be gift-wrapped and delivered from child to parent procedures:

-- Inside NestedProcedure
BEGIN TRY
  -- Procedure logic, twirling its magic wand here
END TRY
BEGIN CATCH
  THROW;  -- Re-gift the error to the ParentProcedure
END CATCH;

-- Inside ParentProcedure
BEGIN TRY
  EXEC NestedProcedure;
END TRY
BEGIN CATCH
  -- Unwrap the gifted error here
  PRINT 'Error from the NestedProcedure. Such a lovely gift. 💝';
END CATCH;
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Conditional Execution

At times you might need to conditionally call a stored procedure, just as we put on a raincoat only when it rains:

IF @Condition = TRUE
BEGIN
  -- "It's raining, put on the raincoat!"
  EXEC NestedProcedure;
END
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