I'm trying to add a simple function in to monetDB at database level, which just does sum(n) and returns the result
create function sys.foo(number int)
returns int
begin
declare tsum int;
set tsum = 0;
while number > 0 do
set tsum = tsum + number;
set number = number -1;
end while;
return tsum;
end;
While attempting to execute the above code i'm seeing error as follows
[Error Code: 0, SQL State: 42000] syntax error, unexpected $end, expecting WHILE: end of input stream in "create function sys.foo(number int)
I could add the same function in to MySQL, and it works!!
>select sys.foo(10)
sys.foo(10)
-----------
55
Could some one please let me know whats going wrong here?
This works fine for me (Oct2014 release of MonetDB, Mac OS X)
➜ ~ mclient
Welcome to mclient, the MonetDB/SQL interactive terminal (unreleased)
Database: MonetDB v11.19.16 (unreleased), 'demo'
Type \q to quit, \? for a list of available commands
auto commit mode: on
sql>create function sys.foo(number int)
more>returns int
more>begin
more>declare tsum int;
more>set tsum = 0;
more>while number > 0 do
more>set tsum = tsum + number;
more>set number = number -1;
more>end while;
more>return tsum;
more>end;
operation successful (2.127ms)
sql>select sys.foo(10);
+------------------+
| foo_single_value |
+==================+
| 55 |
+------------------+
1 tuple (1.771ms)
Related
I'm trying to write a simple ISEMPTY function in Microsoft SQL Server:
DROP FUNCTION IF EXISTS ISEMPTY;
GO
CREATE FUNCTION ISEMPTY
(#charsequence nvarchar(max))
RETURNS BIT
AS
BEGIN
DECLARE #result BIT;
IF (#charsequence IS NULL OR LEN(#charsequence) = 0)
SET #result = 1
ELSE
SET #result = 0;
RETURN #result;
END
GO
When I want to test it with:
SELECT CASE WHEN dbo.ISEMPTY('') THEN 'REACHED!' END;
I get the following error:
[S0001][4145] Line 1: An expression of non-boolean type specified in a context where a condition is expected, near 'THEN'.
What goes wrong here?
A boolean is expected after when in the case expression, but your function returns a bit.
Try this instead:
SELECT CASE WHEN dbo.ISEMPTY('') = 1 THEN 'REACHED!' END;
The function returns a number so you need a comparison with a number to get a boolean value
CREATE FUNCTION ISEMPTY( #charsequence nvarchar(max))
returns BIT AS
begin
DECLARE #result BIT;
IF (#charsequence IS NULL OR LEN(#charsequence) = 0 )
SET #result = 1;
ELSE
SET #result = 0;
RETURN #result;
end
GO
SELECT CASE WHEN dbo.ISEMPTY('') = 1 THEN 'REACHED!' END;
GO
| (No column name) |
| :--------------- |
| REACHED! |
db<>fiddle here
here i'm trying to create a sort of a boolean function but when i try to compile it, it says me that my instruction "truth INTEGER;" is not correct. I can't figure out where does the problem come from because every code sample that i've seen on Google is quite similar to mine. Using Oracle is totally new for me so i'm kinda lost if someone is okay to help me...
I tried a lot of things by searching but nothing works so i'm here to ask for some help...
CODE:
CREATE OR REPLACE FUNCTION HISTOTOX.matching_idipl (iDiplNumero INTEGER) RETURN INTEGER
AS
cpt INTEGER;
truth INTEGER;
BEGIN
SELECT count(*) INTO cpt FROM GARNUCHE.INSC_DIPL WHERE IDIPL_NUMERO = iDiplNumero;
IF cpt = 1 THEN
truth := 1;
ELSE
truth := 0;
END IF;
RETURN truth;
END;
What you reported isn't Oracle error. I replicated your code in my 11g and everything works just fine:
SQL> CREATE OR REPLACE FUNCTION matching_idipl (iDiplNumero INTEGER) RETURN INTEGER
2 AS
3 cpt INTEGER;
4 truth INTEGER;
5
6 BEGIN
7 SELECT count(*) INTO cpt FROM INSC_DIPL WHERE IDIPL_NUMERO = iDiplNumero;
8 IF cpt = 1 THEN
9 truth := 1;
10 ELSE
11 truth := 0;
12 END IF;
13 RETURN truth;
14 END;
15 /
Function created.
SQL> select matching_idipl(1) from dual;
MATCHING_IDIPL(1)
-----------------
1
SQL>
So: where exactly did you execute that code? Which error did you get (exact message and error code, please)?
I have been facing a problem from since morning and have spent many hours but failed to call below given function.
Function definition:
CREATE OR REPLACE FUNCTION public.proc_mc2cdnpf_insertupdatev3(
tblnotesv3 typupdate_notesv3,
tbldoclinks typupdate_guidparameter,
iuserid integer,
shtmltext character varying,
OUT snoteid character varying,
OUT inoteid integer,
OUT inoteactivityid integer)
RETURNS record
LANGUAGE 'plpgsql'
COST 100
VOLATILE
AS $BODY$
#variable_conflict use_variable
declare sNote VARCHAR;
declare sLoggedInUser VARCHAR(20);
declare dtCurrDateTime timestamp;
declare iCurrDate int;
declare iCurrTime INT;
declare iNewNoteID INT;
BEGIN
/*
proc_MC2CDNPF_InsertUpdateV3
2018-04-23 Dennis Sebenick
2018-04-23
- Initial creation of new proc for storing additional HTML text value.
- This proc is going to help bridge the old note system to a new note storage method
2018-04-25
- Added iNoteID / iNoteActivityID for output
2018-06-01
- Update to typUpdate_NotesV3 - removed additional CDN rows for long text
2091-05-08
Rupali Shah
web 1753-added RTRIM(isnull(NOTE_HDQTRS,'')) while creating sNoteID
*/
/******************************
** File: proc_MC2CDNPF_InsertUpdateV3
** Desc: Insert/Update account notes
** Auth: Rupali Shah
** Date: 2019-05-08
**************************
** Change History
**************************
** Date Dev JIRA Description
**2019-05-08 Rupali Shah Web 1753 -added RTRIM(isnull(NOTE_HDQTRS,'')) while creating sNoteID
*******************************/
SELECT dtCurrDateTime = fnGetDate();
SELECT iCurrDate = fnMC2DateToMC2(dtCurrDateTime);
SELECT iCurrTime = fnMC2DateTimeToMC2(dtCurrDateTime);
/*==========================================
Retrieve Update fields from parameter
============================================*/
select
NoteID,
NOTE_NOTES,
NOTE_LOGGEDINUSER,
coalesce(NOTE_ID, 0)
INTO SNoteID,sNote,sLoggedInUser,iNewNoteID
from
tblNotesV3
LIMIT 1;
/************************************************
2018-04-18 DKS
Added in to update new note table
*************************************************/
IF (iNewNoteID > 0)
THEN
BEGIN
IF (LENGTH(sNote) > 0)
THEN
BEGIN
UPDATE
NoteDetails
SET
sNote = sNote,
sNoteHTML = sHTMLText,
iNoteEditedBy = iUserID,
dtNoteEdited = dtCurrDateTime
WHERE
iNoteID = iNewNoteID;
IF (ROWCOUNT = 0)
THEN
BEGIN
INSERT INTO
NoteDetails
(
iNoteType,
sNote,
sNoteHTML,
iNoteEnteredBy,
dtNoteEntered
)
VALUES
( 9, -- iNoteType - int
sNote, -- sNote - VARCHAR(max)
sHTMLText, -- sNoteHTML - VARCHAR(max)
iUserID, -- iNoteEnteredBy - int
dtCurrDateTime
) RETURNING iNewNoteID;
END;
END IF;
END;
END IF;
END;
ELSE
BEGIN
-- Inserting a New Activity
-- 2018-04-18 DKS
-- - Insert to new note table.
IF (LENGTH(sNote) > 0)
THEN
BEGIN
INSERT INTO
NoteDetails
(
iNoteType,
sNote,
sNoteHTML,
iNoteEnteredBy,
dtNoteEntered
)
VALUES
( 9, -- iNoteType - int
sNote, -- sNote - VARCHAR(max)
sHTMLText, -- sNoteHTML - VARCHAR(max)
iUserID, -- iNoteEnteredBy - int
dtCurrDateTime
) RETURNING iNewNoteID;
END;
END IF;
END;
END IF;
/************************************************
End new note table insert / update
*************************************************/
IF EXISTS(SELECT * FROM MC2CDNPF WHERE MC2CDNPF.iNoteID = iNoteID)
THEN
BEGIN
UPDATE
MC2CDNPF
SET
CDNNOTES = '',
CDNFDATE = fnMC2DateToMC2(TblNotesUpdate.NOTE_DDATE),
CDNREASN = TblNotesUpdate.NOTE_REASN,
CDNPRIOR = TblNotesUpdate.NOTE_PRIOR,
CDNTAGGED = TblNotesUpdate.NOTE_TAGGED,
iNoteID = iNewNoteID
FROM
MC2CDNPF
JOIN
tblNotesV3 TblNotesUpdate
ON
MC2CDNPF.iNoteID = TblNotesUpdate.NOTE_ID
WHERE
MC2CDNPF.CDNDSEQN = 1;
END;
ELSE
BEGIN
SELECT
TRIM(coalesce(NOTE_CMPANY,'')) ||
TRIM(coalesce(NOTE_BUSNSS,'')) ||
TRIM(coalesce(NOTE_CUSNBR,'')) ||
TRIM(coalesce(NOTE_ENTITY,'')) ||
TRIM(coalesce(NOTE_HDQTRS,'')) ||
CAST( iCurrDate AS VARCHAR(8)) ||
CAST( iCurrTime AS VARCHAR(10))
INTO sNoteID
FROM
tblNotesV3
LIMIT 1;
INSERT INTO
MC2CDNPF
(
CDNDSEQN,
CDNNOTES,
CDNCMPANY,
CDNCUSNBR,
CDNBUSNSS,
CDNENTITY,
CDNHDQTRS,
CDNRPTCON,
CDNFULNME,
CDNAGNIDN,
CDNDDATE,
CDNDTIME,
CDNREASN,
CDNTUSER,
CDNADATE,
CDNTAGGED,
CDNFDATE,
CDNPRIOR,
CDNDTASRC,
CDNODATE,
CDNOTIME,
iNoteID
)
SELECT
1,
'', -- 6/1/2018 DKS - no longer storing note in MC2CDNPF
coalesce(NOTE_CMPANY,''),
coalesce(NOTE_CUSNBR,''),
coalesce(NOTE_BUSNSS,''),
coalesce(NOTE_ENTITY,''),
coalesce(NOTE_HDQTRS,''),
coalesce(NOTE_RPTCON,''),
NOTE_FULNME,
coalesce(NOTE_AGNIDN,''),
iCurrDate,
iCurrTime,
NOTE_REASN,
NOTE_TUSER,
iCurrDate,
coalesce(NOTE_TAGGED,''),
iCurrDate,
NOTE_PRIOR,
coalesce(NOTE_DTASRC,''),
iCurrDate,
iCurrTime,
iNewNoteID
FROM
tblNotesV3 TblSource;
END;
END IF;
-- There are attachments to link
IF EXISTS(SELECT * FROM tblDocLinks)
THEN
BEGIN
CALL public.proc_Documents_AddLinkMultiple_LinkID (tblDocLinks, 9, 0, sNoteID, iUserID);
END;
END IF;
iNoteID := iNewNoteID;
iNoteActivityID := 0;
END;
$BODY$;
I am trying to call my function in following two ways:
Method1:
SELECT public.proc_MC2CDNPF_InsertUpdateV3
(
(SELECT w::typupdate_notesv3 FROM (TABLE tblnotesv31) w ) ,
(SELECT w1::typupdate_guidparameter FROM (TABLE tbldoclinks1) w1 ) ,
1,
'test text'
)
But it fails with following error:
ERROR: query has no destination for result data
HINT: If you want to
discard the results of a SELECT, use PERFORM instead. CONTEXT:
PL/pgSQL function
proc_mc2cdnpf_insertupdatev3(typupdate_notesv3,typupdate_guidparameter,integer,character
varying) line 41 at SQL statement SQL state: 42601
Method2:
SELECT *
from proc_MC2CDNPF_InsertUpdateV3
(
(SELECT w::typupdate_notesv3 FROM (TABLE tblnotesv31) w ) ,
(SELECT w1::typupdate_guidparameter FROM (TABLE tbldoclinks1) w1 ) ,
1,
'test text'
)
Again it failed saying:
ERROR: query has no destination for result data HINT: If you want to
discard the results of a SELECT, use PERFORM instead. CONTEXT:
PL/pgSQL function
proc_mc2cdnpf_insertupdatev3(typupdate_notesv3,typupdate_guidparameter,integer,character
varying) line 41 at SQL statement SQL state: 42601
Can please someone help me out that what's actually wrong with my function call?
Starting at line 41 (as the error message told you) you got:
SELECT dtCurrDateTime = fnGetDate();
SELECT iCurrDate = fnMC2DateToMC2(dtCurrDateTime);
SELECT iCurrTime = fnMC2DateTimeToMC2(dtCurrDateTime);
I assume you want to set the variables there. But you're doing it wrong. (It looks like you tried to use SQL Server syntax. Is this an attempt to port a function from SQL Server to Postgres? There are also BEGIN ... END blocks for IFs and ELSEs, which are unnecessary (but harmless) in Postgres but needed in SQL Server.)
Either use INTO:
SELECT fnGetDate() INTO dtCurrDateTime;
SELECT fnMC2DateToMC2(dtCurrDateTime) INTO iCurrDate;
SELECT fnMC2DateTimeToMC2(dtCurrDateTime) INTO iCurrTime;
Or, since you're not actually querying a table, simple assignments should work too:
dtCurrDateTime = fnGetDate();
iCurrDate = fnMC2DateToMC2(dtCurrDateTime);
iCurrTime = fnMC2DateTimeToMC2(dtCurrDateTime);
There might be other lines with the same mistake, you should check the whole code.
I've seen a bunch of different solutions on StackOverflow that span many years and many Postgres versions, but with some of the newer features like gen_random_bytes I want to ask again to see if there is a simpler solution in newer versions.
Given IDs which contain a-zA-Z0-9, and vary in size depending on where they're used, like...
bTFTxFDPPq
tcgHAdW3BD
IIo11r9J0D
FUW5I8iCiS
uXolWvg49Co5EfCo
LOscuAZu37yV84Sa
YyrbwLTRDb01TmyE
HoQk3a6atGWRMCSA
HwHSZgGRStDMwnNXHk3FmLDEbWAHE1Q9
qgpDcrNSMg87ngwcXTaZ9iImoUmXhSAv
RVZjqdKvtoafLi1O5HlvlpJoKzGeKJYS
3Rls4DjWxJaLfIJyXIEpcjWuh51aHHtK
(Like the IDs that Stripe uses.)
How can you generate them randomly and safely (as far as reducing collisions and reducing predictability goes) with an easy way to specify different lengths for different use cases, in Postgres 9.6+?
I'm thinking that ideally the solution has a signature similar to:
generate_uid(size integer) returns text
Where size is customizable depending on your own tradeoffs for lowering the chance of collisions vs. reducing the string size for usability.
From what I can tell, it must use gen_random_bytes() instead of random() for true randomness, to reduce the chance that they can be guessed.
Thanks!
I know there's gen_random_uuid() for UUIDs, but I don't want to use them in this case. I'm looking for something that gives me IDs similar to what Stripe (or others) use, that look like: "id": "ch_19iRv22eZvKYlo2CAxkjuHxZ" that are as short as possible while still containing only alphanumeric characters.
This requirement is also why encode(gen_random_bytes(), 'hex') isn't quite right for this case, since it reduces the character set and thus forces me to increase the length of the strings to avoid collisions.
I'm currently doing this in the application layer, but I'm looking to move it into the database layer to reduce interdependencies. Here's what the Node.js code for doing it in the application layer might look like:
var crypto = require('crypto');
var set = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
function generate(length) {
var bytes = crypto.randomBytes(length);
var chars = [];
for (var i = 0; i < bytes.length; i++) {
chars.push(set[bytes[i] % set.length]);
}
return chars.join('');
}
Figured this out, here's a function that does it:
CREATE OR REPLACE FUNCTION generate_uid(size INT) RETURNS TEXT AS $$
DECLARE
characters TEXT := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
bytes BYTEA := gen_random_bytes(size);
l INT := length(characters);
i INT := 0;
output TEXT := '';
BEGIN
WHILE i < size LOOP
output := output || substr(characters, get_byte(bytes, i) % l + 1, 1);
i := i + 1;
END LOOP;
RETURN output;
END;
$$ LANGUAGE plpgsql VOLATILE;
And then to run it simply do:
generate_uid(10)
-- '3Rls4DjWxJ'
Warning
When doing this you need to be sure that the length of the IDs you are creating is sufficient to avoid collisions over time as the number of objects you've created grows, which can be counter-intuitive because of the Birthday Paradox. So you will likely want a length greater (or much greater) than 10 for any reasonably commonly created object, I just used 10 as a simple example.
Usage
With the function defined, you can use it in a table definition, like so:
CREATE TABLE users (
id TEXT PRIMARY KEY DEFAULT generate_uid(10),
name TEXT NOT NULL,
...
);
And then when inserting data, like so:
INSERT INTO users (name) VALUES ('ian');
INSERT INTO users (name) VALUES ('victor');
SELECT * FROM users;
It will automatically generate the id values:
id | name | ...
-----------+--------+-----
owmCAx552Q | ian |
ZIofD6l3X9 | victor |
Usage with a Prefix
Or maybe you want to add a prefix for convenience when looking at a single ID in the logs or in your debugger (similar to how Stripe does it), like so:
CREATE TABLE users (
id TEXT PRIMARY KEY DEFAULT ('user_' || generate_uid(10)),
name TEXT NOT NULL,
...
);
INSERT INTO users (name) VALUES ('ian');
INSERT INTO users (name) VALUES ('victor');
SELECT * FROM users;
id | name | ...
---------------+--------+-----
user_wABNZRD5Zk | ian |
user_ISzGcTVj8f | victor |
I'm looking for something that gives me "shortcodes" (similar to what Youtube uses for video IDs) that are as short as possible while still containing only alphanumeric characters.
This is a fundamentally different question from what you first asked. What you want here then is to put a serial type on the table, and to use hashids.org code for PostgreSQL.
This returns 1:1 with the unique number (serial)
Never repeats or has a chance of collision.
Also base62 [a-zA-Z0-9]
Code looks like this,
SELECT id, hash_encode(foo.id)
FROM foo; -- Result: jNl for 1001
SELECT hash_decode('jNl') -- returns 1001
This module also supports salts.
Review,
26 characters in [a-z]
26 characters in [A-Z]
10 characters in [0-9]
62 characters in [a-zA-Z0-9] (base62)
The function substring(string [from int] [for int]) looks useful.
So it looks something like this. First we demonstrate that we can take the random-range and pull from it.
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
1, -- 1 is 'a', 62 is '9'
1,
);
Now we need a range between 1 and 63
SELECT trunc(random()*62+1)::int+1
FROM generate_series(1,1e2) AS gs(x)
This gets us there.. Now we just have to join the two..
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1
1
)
FROM generate_series(1,1e2) AS gs(x);
Then we wrap it in an ARRAY constructor (because this is fast)
SELECT ARRAY(
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1,
1
)
FROM generate_series(1,1e2) AS gs(x)
);
And, we call array_to_string() to get a text.
SELECT array_to_string(
ARRAY(
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1,
1
)
FROM generate_series(1,1e2) AS gs(x)
)
, ''
);
From here we can even turn it into a function..
CREATE FUNCTION random_string(randomLength int)
RETURNS text AS $$
SELECT array_to_string(
ARRAY(
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1,
1
)
FROM generate_series(1,randomLength) AS gs(x)
)
, ''
)
$$ LANGUAGE SQL
RETURNS NULL ON NULL INPUT
VOLATILE LEAKPROOF;
and then
SELECT * FROM random_string(10);
Thanks to Evan Carroll answer, I took a look on hashids.org.
For Postgres you have to compile the extension or run some TSQL functions.
But for my needs, I created something simpler based on hashids ideas (short, unguessable, unique, custom alphabet, avoid curse words).
Shuffle alphabet:
CREATE OR REPLACE FUNCTION consistent_shuffle(alphabet TEXT, salt TEXT) RETURNS TEXT AS $$
DECLARE
SALT_LENGTH INT := length(salt);
integer INT = 0;
temp TEXT = '';
j INT = 0;
v INT := 0;
p INT := 0;
i INT := length(alphabet) - 1;
output TEXT := alphabet;
BEGIN
IF salt IS NULL OR length(LTRIM(RTRIM(salt))) = 0 THEN
RETURN alphabet;
END IF;
WHILE i > 0 LOOP
v := v % SALT_LENGTH;
integer := ASCII(substr(salt, v + 1, 1));
p := p + integer;
j := (integer + v + p) % i;
temp := substr(output, j + 1, 1);
output := substr(output, 1, j) || substr(output, i + 1, 1) || substr(output, j + 2);
output := substr(output, 1, i) || temp || substr(output, i + 2);
i := i - 1;
v := v + 1;
END LOOP;
RETURN output;
END;
$$ LANGUAGE plpgsql VOLATILE;
The main function:
CREATE OR REPLACE FUNCTION generate_uid(id INT, min_length INT, salt TEXT) RETURNS TEXT AS $$
DECLARE
clean_alphabet TEXT := 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
curse_chars TEXT := 'csfhuit';
curse TEXT := curse_chars || UPPER(curse_chars);
alphabet TEXT := regexp_replace(clean_alphabet, '[' || curse || ']', '', 'gi');
shuffle_alphabet TEXT := consistent_shuffle(alphabet, salt);
char_length INT := length(alphabet);
output TEXT := '';
BEGIN
WHILE id != 0 LOOP
output := output || substr(shuffle_alphabet, (id % char_length) + 1, 1);
id := trunc(id / char_length);
END LOOP;
curse := consistent_shuffle(curse, output || salt);
output := RPAD(output, min_length, curse);
RETURN output;
END;
$$ LANGUAGE plpgsql VOLATILE;
How-to use examples:
-- 3: min-length
select generate_uid(123, 3, 'salt'); -- output: "0mH"
-- or as default value in a table
CREATE SEQUENCE IF NOT EXISTS my_id_serial START 1;
CREATE TABLE collections (
id TEXT PRIMARY KEY DEFAULT generate_uid(CAST (nextval('my_id_serial') AS INTEGER), 3, 'salt')
);
insert into collections DEFAULT VALUES ;
This query generate required string. Just change second parasmeter of generate_series to choose length of random string.
SELECT
string_agg(c, '')
FROM (
SELECT
chr(r + CASE WHEN r > 25 + 9 THEN 97 - 26 - 9 WHEN r > 9 THEN 64 - 9 ELSE 48 END) AS c
FROM (
SELECT
i,
(random() * 60)::int AS r
FROM
generate_series(0, 62) AS i
) AS a
ORDER BY i
) AS A;
So I had my own use-case for something like this. I am not proposing a solution to the top question, but if you are looking for something similar like I am, then try this out.
My use-case was that I needed to create a random external UUID (as a primary key) with as few characters as possible. Thankfully, the scenario did not have a requirement that a large amount of these would ever be needed (probably in the thousands only). Therefore a simple solution was a combination of using generate_uid() and checking to make sure that the next sequence was not already used.
Here is how I put it together:
CREATE OR REPLACE FUNCTION generate_id (
in length INT
, in for_table text
, in for_column text
, OUT next_id TEXT
) AS
$$
DECLARE
id_is_used BOOLEAN;
loop_count INT := 0;
characters TEXT := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
loop_length INT;
BEGIN
LOOP
next_id := '';
loop_length := 0;
WHILE loop_length < length LOOP
next_id := next_id || substr(characters, get_byte(gen_random_bytes(length), loop_length) % length(characters) + 1, 1);
loop_length := loop_length + 1;
END LOOP;
EXECUTE format('SELECT TRUE FROM %s WHERE %s = %s LIMIT 1', for_table, for_column, quote_literal(next_id)) into id_is_used;
EXIT WHEN id_is_used IS NULL;
loop_count := loop_count + 1;
IF loop_count > 100 THEN
RAISE EXCEPTION 'Too many loops. Might be reaching the practical limit for the given length.';
END IF;
END LOOP;
END
$$
LANGUAGE plpgsql
STABLE
;
here is an example table usage:
create table some_table (
id
TEXT
DEFAULT generate_id(6, 'some_table', 'id')
PRIMARY KEY
)
;
and a test to see how it breaks:
DO
$$
DECLARE
loop_count INT := 0;
BEGIN
-- WHILE LOOP
WHILE loop_count < 1000000
LOOP
INSERT INTO some_table VALUES (DEFAULT);
loop_count := loop_count + 1;
END LOOP;
END
$$ LANGUAGE plpgsql
;
I found this code snipped (Source):
CREATE PROCEDURE rec_fib(n INT, OUT out_fib INT)
BEGIN
DECLARE n_1 INT;
DECLARE n_2 INT;
IF (n=0) THEN
SET out_fib=0;
ELSEIF (n=1) then
SET out_fib=1;
ELSE
CALL rec_fib(n-1,n_1);
CALL rec_fib(n-2,n_2);
SET out_fib=(n_1 + n_2);
END IF;
END
This code works with MySQL. In how far do I have to modify it to run on DB2? I cannot seem to find a running minimal example of an recursive stored procedure for DB2.
This works for me: (I haven't done more than make it work, so alternative coding could also work.)
First, add these two lines:
DECLARE n_3 INT;
DECLARE n_4 INT;
Then modify this small section:
ELSE
set n_3 = n - 1;
set n_4 = n - 2;
CALL rec_fib(n_3,n_1);
CALL rec_fib(n_4,n_2);
That's all. Runs on IBM i 6.1 DB2 UDB.
The following code is from SQL tips for DB2, written by Serge Rielau
CREATE OR REPLACE FUNCTION Fib(n INTEGER) RETURNS DECIMAL(31, 0)
BEGIN
DECLARE res DECIMAL(31, 0);
CASE WHEN n = 0 THEN
SET res = 0;
WHEN n = 1 THEN
SET res = 1;
WHEN n > 1 THEN
BEGIN
DECLARE stmt STATEMENT;
PREPARE stmt FROM 'SET ? = Fib(? - 1) + Fib(? - 2)';
EXECUTE stmt INTO res USING n, n;
END;
ELSE
SIGNAL SQLSTATE '78000' SET MESSAGE_TEXT = 'Bad input';
END CASE;
RETURN res;
END;
/
For more information, please check the source page of this code: https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/recursive_sql_pl?lang=en