This document discusses the evolution of user-defined functions (UDFs) in Oracle SQL over multiple Oracle database versions. It shows how UDFs started as PL/SQL functions callable from SQL in earlier versions, which could impact performance. It then demonstrates how newer Oracle database versions allow defining UDFs directly in SQL for improved performance and maintainability when using functions in SQL statements and queries. The document provides examples of different ways to implement and call UDFs across various Oracle versions.

1. 1
12c

2. 2
the focus ...
the day to day stuff

3. Feature
inline PLSQL in SQL

4. most systems ...

5. ... I've worked on

6. struggles with case

7. no correlation :-)

8. SQL> select vendor
2 from service_provider;
VENDOR
------------------------------
jones
brown
SMITH
sigh...

9. "no problem.... I'll use initcap"

10. SQL> select initcap(vendor)
2 from service_provider;
INITCAP(VENDOR)
------------------------------
Jones
Brown
Smith

11. until ...

12. SQL> select initcap(vendor)
2 from service_provider;
INITCAP(VENDOR)
------------------------------
Jones
Brown
Smith
Mcdonald
Johnson'S
uh oh

13. home grown

14. SQL> create or replace
2 function my_initcap(p_string varchar2) return varchar2 is
3 l_string varchar2(1000) := p_string;
4 begin
5 if regexp_like(l_string,'(Mac[A-Z]|Mc[A-Z])') then
6 null;
7 elsif l_string like '''%' then
8 null;
9 else
10 l_string := initcap(l_string);
11 if l_string like '_''S%' then
12 null;
13 else
14 l_string := replace(l_string,'''S','''s');
15 end if;
16 end if;
17
18 return l_string;
19 end;
20 /
Function created.

15. cool ...

16. SQL> select my_initcap(vendor)
2 from service_provider;
MY_INITCAP(VENDOR)
--------------------------
Jones
Brown
Smith
McDonald
Johnson's

17. until ...

19. "how dare you developer...
don't call PLSQL from SQL !!!!"

20. SQL> select max(x)
2 from (
3 select /*+ no_merge */ initcap(source) x
4 from large_table
5 );
...
Elapsed: 00:00:00.48
SQL> select max(x)
2 from (
3 select /*+ no_merge */ my_initcap(source) x
4 from large_table
5 );
Elapsed: 00:00:09.37

21. it can be done in SQL

22. SQL> select
2 case
3 when regexp_like(vendor,'(Mac[A-Z]|Mc[A-Z])') then vendor
4 when vendor like '''%' then vendor
5 when initcap(vendor) like '_''S%' then vendor
6 else replace(initcap(vendor),'''S','''s')
7 end ugh
8 from service_provider;
UGH
-------------------------------
Jones
Brown
Smith
McDonald
Johnson's

23. maintenance nightmare

24. 12c ... user defined functions

25. SQL> WITH
2 function my_initcap(p_string varchar2)
3 return varchar2 is
4 l_string varchar2(1000) := p_string;
5 begin
6 if regexp_like(l_string,'(Mac[A-Z]|Mc[A-Z])') then
7 null;
8 elsif l_string like '''%' then
...
17
18 return l_string;
19 end;
20 select my_initcap(vendor)
21 from service_provider;
MY_INITCAP(VENDOR)
-----------------------------------------
Jones
Brown
Smith
McDonald
O'Brien
Johnson's

26. multiple routines

27. SQL> WITH
2 function is_scottish(p_string varchar2) return boolean is
3 begin
4 return regexp_like(p_string,'(Mac[A-Z]|Mc[A-Z])');
5 end;
6 function my_initcap(p_string varchar2) return varchar2 is
7 l_string varchar2(1000) := p_string;
8 begin
9 if is_scottish(l_string) then
10 null;
11 elsif l_string like '''%' then
12 null;
13 else
14 l_string := initcap(l_string);
15 if l_string like '_''S%' then
16 null;
17 else
18 l_string := replace(l_string,'''S','''s');
19 end if;
20 end if;
21
22 return l_string;
23 end;
24 select my_initcap(surname)
25 from names;
26 /

28. note: 12c client

29. 11.2 and below

30. SQL> WITH
2 function my_initcap(p_string varchar2) return varchar2 is
3 l_string varchar2(1000) := p_string;
function my_initcap(p_string varchar2) return varchar2 is
*
ERROR at line 2:
ORA-06553: PLS-103: Encountered the symbol "end-of-file" when
expecting one of the following:
. ( * @ % & = - + ; < / > at in is mod remainder not rem
<an exponent (**)> <> or != or ~= >= <= <> and or like like2
like4 likec between || multiset member submultiset
SQL> begin
2 if regexp_like(l_string,'(Mac[A-Z]|Mc[A-Z])') then
3 null;
4 elsif l_string like '''%' then
5 null;
6 else
7 l_string := initcap(l_string);

31. some catch up coming #1

32. SQL> create or replace
2 procedure NAMES_PROCESSOR is
3 cursor C is
4 WITH
5 function my_initcap(p_string varchar2)
return varchar2 is
6 l_string varchar2(1000) := p_string;
7 begin
...
23 select my_initcap(vendor) from service_provider;
25 begin
26 null;
27 end;
28 /
Warning: Procedure created with compilation errors.
SQL> sho err
Errors for PROCEDURE NAMES_PROCESSOR:
LINE/COL ERROR
-------- ------------------------------------------------
3/7 PL/SQL: SQL Statement ignored
4/18 PL/SQL: ORA-00905: missing keyword
22/7 PLS-00103: Encountered the symbol "SELECT"

33. SQL> create or replace
2 procedure NAMES_PROCESSOR is
3 rc sys_refcursor;
4 begin
5 open rc for
6 q'{ WITH
7 function my_initcap(p_string varchar2)
return varchar2 is
8 l_string varchar2(1000) := p_string;
9 begin
...
23 return l_string;
24 end;
25 select my_initcap(vendor)
26 from service_provider
27 }';
28 end;
29 /
Procedure created.

34. some catch up coming #2

35. WITH_PLSQL
unrelated to previous

36. DML (or complex SQL)

37. SQL> insert into CONTRACTS
2 WITH
3 function my_initcap(p_string varchar2)
4 return varchar2 is
5 l_string varchar2(1000) := p_string;
6 begin
...
20 end;
21 select my_initcap(vendor)
22 from service_provider;
23 /
WITH
*
ERROR at line 2:
ORA-32034: unsupported use of WITH clause

38. SQL> insert /*+ WITH_PLSQL */ into CONTRACTS
2 WITH
3 function my_initcap(p_string varchar2)
4 return varchar2 is
5 l_string varchar2(1000) := p_string;
6 begin
...
20 end;
21 select my_initcap(surname)
22 from names;
23 /
5 rows inserted.

39. determinism

40. SQL> with
2 function f return timestamp as
3 begin
4 return systimestamp;
5 end;
6 select f
7 from dual
8 connect by level <= 10;
9 /
F
----------------------------------------
05-JAN-14 08.09.43.969000000 PM
05-JAN-14 08.09.43.970000000 PM
05-JAN-14 08.09.43.970000000 PM
05-JAN-14 08.09.43.971000000 PM
...

41. DETERMINISTIC keyword

42. SQL> with
2 function f return timestamp DETERMINISTIC as
3 begin
4 return systimestamp;
5 end;
6 select f
7 from dual
8 connect by level <= 10;
9 /
F
----------------------------------------
05-JAN-14 08.09.52.145000000 PM
05-JAN-14 08.09.52.146000000 PM
05-JAN-14 08.09.52.146000000 PM
05-JAN-14 08.09.52.147000000 PM
...

43. conventional scalar caching

44. SQL> with
2 function f return timestamp as
3 begin
4 return systimestamp;
5 end;
6 select ( select f from dual )
7 from dual
8 connect by level <= 10;
9 /
F
----------------------------------------
05-JAN-14 08.11.50.145000000 PM
05-JAN-14 08.11.50.145000000 PM
05-JAN-14 08.11.50.145000000 PM
05-JAN-14 08.11.50.145000000 PM
...

45. are they really faster ?

46. SQL> create or replace
2 function F return number is
3 begin
4 return 1;
5 end;
6 /
Function created.

47. SQL> select sum(f)
2 from
3 ( select level from dual
4 connect by level <= 1000 ),
5 ( select level from dual
6 connect by level <= 1000 )
7 ;
SUM(F)
----------
1000000
Elapsed: 00:00:02.04

48. SQL> with
2 function f1 return number is
3 begin
4 return 1;
5 end;
6 select sum(f1)
7 from
8 ( select level from dual
9 connect by level <= 1000 ),
10 ( select level from dual
11 connect by level <= 1000 )
12 /
SUM(F1)
----------
1000000
Elapsed: 00:00:00.52

49. "but what about all my PLSQL !!!"

50. SQL> create or replace
2 function F return number is
3 pragma udf;
4 begin
5 return 1;
6 end;
SQL> select sum(f)
2 from
3 ( select level from dual
4 connect by level <= 1000 ),
5 ( select level from dual
6 connect by level <= 1000 );
SUM(F)
----------
1000000
Elapsed: 00:00:00.36