MSSQL to PostgreSQL - Issue trying to generate unique ID using actual date

Hi all,

I am facing a problem trying to convert from MSSQL procedure to PostgreSQL
function.

CREATE PROCEDURE dbo.THUBAN_SP_GENERATEID

@NEWID VARCHAR(20) OUTPUT

AS

SET @NEWID = (

SELECT
REPLACE(SUBSTRING(CONVERT(CHAR(10),GETDATE(),20 ),1,10),'-','')

+ CAST(REPLICATE(0,8-LEN
(ISNULL(CAST(SUBSTRING(MAX(SEQ_ID),9,8) AS

INTEGER),0) + 1)) AS VARCHAR)

+
CAST(ISNULL(CAST(SUBSTRING(MAX(SEQ_ID),9,8) AS INTEGER),0) + 1 AS

VARCHAR)

FROM THUBAN_SEQ

WHERE SUBSTRING(SEQ_ID,1,8)=

REPLACE(SUBSTRING(CONVERT(CHAR(10),GETDATE(),20 ),1,10),'-','')

)

INSERT INTO THUBAN_SEQ VALUES (@NEWID)

SELECT @NEWID AS ITEM_ID;

GO

This is what I made,

CREATE OR REPLACE FUNCTION THUBAN_SP_GENERATEID()

RETURNS VARCHAR

AS $$

DECLARE NEWID VARCHAR;

DECLARE SEQID VARCHAR;

BEGIN

SELECT INTO NEWID TO_CHAR(CURRENT_DATE::DATE, 'YYYYMMDD');

-- IF EXISTS A ROW IN THE TABLE STARTING WITH THE
CURRENT_DATE, SELECT THE MAX OF THEM.

IF EXISTS(SELECT(MAX(SEQ_ID)) FROM THUBAN_SEQ WHERE SEQ_ID
LIKE (SELECT TO_CHAR(CURRENT_DATE::DATE, 'YYYYMMDD') || '%')) THEN

SELECT INTO NEWID ((SELECT(MAX(SEQID)) FROM
THUBAN_SEQ WHERE SEQ_ID LIKE NEWID || '%') + 1);

ELSE

-- THIS IS NOT RIGHT AT ALL, RIGHT? HOW CAN I
DO TO CONCATENATE AN INTEGER NUMBER LIKE 14 + SOME NUMBER OF 0 BEFORE?

SEQID := '00000001';

NEWID := NEWID + SEQID;

END IF;

RETURN NEWID;

END;

$$ LANGUAGE plpgsql;

SELECT THUBAN_SP_GENERATEID();

Beside this, there is something than I would like to ask than I couldn't
find. How can I do to set a variable in a way like this as MSSQL does:

SET @NEWID = (SELECT..

And not doing SELECT INTO VARIABLE_TO_SET (SELECT...

All comments will be welcome, I am pretty new with PostgreSQL but I find It
very interesting.

Thanks & Regards,

Ignacio