SQL SERVER – Difference Between EXEC and EXECUTE vs EXEC() – Use EXEC/EXECUTE for SP always

What is the difference between EXEC and EXECUTE?

They are the same. Both of them executes stored procedure when called as
EXEC sp_help
GO
EXECUTE sp_help
GO

I have seen enough times developer getting confused between EXEC and EXEC(). EXEC command executes stored procedure where as EXEC() function takes dynamic string as input and executes them.
EXEC('EXEC sp_help')
GO

Another common mistakes I have seen is not using EXEC before stored procedure. It is always good practice to use EXEC before stored procedure name even though SQL Server assumes any command as stored procedure when it does not recognize the first statement. Developer learns while working with Query Editor in SSMS that EXEC is not necessary before running any stored procedure. However, consider following two test and you will see why EXEC or EXECUTE is necessary in many cases and good practice to use it.

TEST 1 : No Errors
USE AdventureWorks;
GO
----Try this first independently this will throw an error
sp_helptext 'dbo.uspPrintError'
GO
----Try this second independently this will work fine
EXEC sp_helptext 'dbo.uspPrintError'
GO

TEST 2 : EXEC prevents error
USE AdventureWorks;
GO
----Try this first independently this will throw an error
SELECT *
FROM Sales.Individual
sp_helptext 'dbo.uspPrintError'
GO
----Try this second independently this will work fine
SELECT *
FROM Sales.Individual
EXEC sp_helptext 'dbo.uspPrintError'
GO