Execute STORED PROCEDURE FROM A FUNCTION

sql

sqlclr

stored-procedures

dynamic-sql

byAnton Shumikhin·Oct 9, 2024

-- Let's cheat the boss with a wrap party
CREATE PROCEDURE CallMyStoredProcedure
AS
BEGIN
    -- Don't tell my function I'm here!
    EXEC MyActualStoredProcedure
END

Functions can't execute stored procedures, due to their deterministic nature and no-side-effects policy. To bypass this, put on a disguise as a stored procedure or rendezvous via a table-valued function using OPENROWSET.

-- The KGB agent in the midst 
CREATE FUNCTION dbo.AccessStoredProcedureData()
RETURNS TABLE
AS
RETURN 
(
    SELECT * FROM OPENROWSET('SQLNCLI', 'Server=(local);Trusted_Connection=yes;',
    'EXEC MyDatabase.dbo.MyStoredProcedure')
)

Beware, OPENROWSET requires ad hoc distributed queries on your SQL Server, possibly restricted by your DBA for a 'no leakage' policy.

Infiltration: SQLCLR

To outsmart the FUNCTION overlords, consider recruiting a CLR-based taskforce with managed code. This contingent called SQLCLR (SQL Common Language Runtime) can execute stored procedures from within user-defined functions, and also provides an access pass to session-based object with the "context connection = true" setting.

Just like in any covert operation, there are unforeseen constraints such as inconsistent execution that could occur during multi-row operation scenarios. The word of caution is to always prioritize security whilst implementing SQLCLR, utilizing the security features like code access security can help minimize the risks.

The Undercover Agent: Dynamic SQL

Our toolkit also contains an alias strategy—Dynamic SQL within stored procedures. You can emulate function-like behaviours using dynamically executed intelligence:

-- Feeding inside information stealthily
CREATE PROCEDURE SimulateFunctionBehavior
AS
BEGIN
    -- The chameleon code 
    DECLARE @DynamicSQL NVARCHAR(MAX)
    SET @DynamicSQL = N'SELECT * FROM MyTable WHERE ...' -- Dynamic intel part
    EXEC sp_executesql @DynamicSQL
END

The EXEC() command is the Covert op expert that can execute the dynamically morphed operations, simulating the read-only aspect of a function with the rogue power of a stored procedure. Although Extended Stored Procedures pack a punch, it's best to stay stealth and favor more secure alternatives.

The Operative Directives

SQL Functions are the quiet intelligence hubs delivering core computation outputs. Trying to dress them as the action heroes (Stored Procedures) endangers their design intent, leading to blurred lines between the deterministic and the operational roles.

While these workarounds fundamentally prioritize efficiency & security, tread lightly while navigating the alleys of linked servers and OPENQUERY. They might present unanticipated and significant security exposures.

Remember, even the best operatives work within protocol and understand the implications.

explain-codes / Sql / Execute STORED PROCEDURE FROM A FUNCTION

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