SQL SERVER - SQL Server BUG Set "-defined functions and group by"SQL SERVER,bug

SQL Server BUG Set “-defined functions and group by”

/**==** 1. Custom function for the group by error **==**/
— A simple function
Create function f_str (@ str sysname, @ i int)
Returns char (1)
As begin
Return (substring (str @, @ i, 1))
End
Go

— Below are the test

— Definition of the test data
Declare @ t table (name sysname)
Insert into @ t values ( 'abcd')

— A group by the situation, the wrong results
Select a = dbo.f_str (name, 1), b = dbo.f_str (name, 2)
From @ t
Group by dbo.f_str (name, 1), dbo.f_str (name, 2)

— No group by the situation, the correct results
Select a = dbo.f_str (name, 1), b = dbo.f_str (name, 2)
From @ t
Go

— Delete test-defined functions
Drop function f_str

/ Op test results
A b
—- —-
A a

(Number of rows affected by the line 1)

A b
—- —-
A b

(Number of rows affected by the line 1)
–* /

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