SQL Server 2017

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CREATE TABLE List_of_Functions(functionid INT);
INSERT INTO List_of_functions(functionid) VALUES(1),(2),(3),(4);
4 rows affected

CREATE FUNCTION Function_1()
RETURNS VARCHAR(100)
AS
BEGIN
   RETURN 'Return from Function_1';
END;
CREATE FUNCTION Function_2()
RETURNS VARCHAR(100)
AS
BEGIN
   RETURN 'Return from Function_2';
END;
CREATE FUNCTION Function_3()
RETURNS VARCHAR(100)
AS
BEGIN
   RETURN 'Return from Function_3';
END;
CREATE FUNCTION Function_dispatcher(@name SYSNAME)
RETURNS VARCHAR(100)
AS
BEGIN
  DECLARE @r VARCHAR(100);
  IF OBJECT_ID(@name, N'FN') IS NULL
    RETURN NULL;
  EXEC @r = @name; 
  RETURN @r;
END;
SELECT *, dbo.Function_dispatcher(s.n) AS result
FROM List_of_Functions lf
OUTER APPLY(SELECT CONCAT('dbo.Function_', lf.functionid)) s(n)


functionid
n
result


1
dbo.Function_1
Return from Function_1

2
dbo.Function_2
Return from Function_2

3
dbo.Function_3
Return from Function_3

4
dbo.Function_4
null

functionid	n	result
1	dbo.Function_1	Return from Function_1
2	dbo.Function_2	Return from Function_2
3	dbo.Function_3	Return from Function_3
4	dbo.Function_4	null