adding '1' returns "BLOB" - mysql

Question

A JobID goes as follows: ALC-YYYYMMDD-001. The first three are a companies initials, the last three are an incrementing number that resets daily and increments throughout the day as jobs are added for a maximum of 999 jobs in a day; it is these last three that I am trying to work with.
I am trying to get a before-insert trigger to look for the max JobID of the day, and add one so I can have the trigger derive the proper JobID. For the first job, it will of course return null. So here is what I have so far.
Through the following I can get a result of '000'.
set #maxjobID =
(select SUBSTRING(
(Select MAX(
SUBSTRING((Select JobID FROM jobs WHERE SUBSTRING(JobID,5,8)=date_format(curdate(), '%Y%m%d')),4,12)
)
),14,3)
);
select lpad((select ifnull(#maxjobID,0)),3,'0')
But I really need to add one to this keeping the leading zeros to increment the first and subsequent jobs of the day. My problem is as soon as try to add '1' I get a return of 'BLOB'. That is:
select lpad((select ifnull(#maxjobID,0)+1),3,'0')
returns 'BLOB'
I need it to return '001' so I can concatenate that result with the CO initials and the current date.

Answer 1

try casting VARCHAR back to INTEGER
SELECT lpad(SELECT (COALESCE(#maxjobID,0, CAST(#maxjobID AS SIGNED)) + 1),3,'0')

Answer 2

If you're using the MyISAM storage engine, you can implement exactly this with AUTO_INCREMENT, without denormalising your data into a delimited string:
For MyISAM tables, you can specify AUTO_INCREMENT on a secondary column in a multiple-column index. In this case, the generated value for the AUTO_INCREMENT column is calculated as MAX(auto_increment_column) + 1 WHERE prefix=given-prefix. This is useful when you want to put data into ordered groups.
In your case:
Normalise your schema:
ALTER TABLE jobs
ADD initials CHAR(3) NOT NULL FIRST,
ADD date DATE NOT NULL AFTER initials,
ADD seq SMALLINT(3) UNSIGNED NOT NULL AFTER date,
;
Normalise your existing data:
UPDATE jobs SET
initials = SUBSTRING_INDEX(JobID, '-', 1),
date = STR_TO_DATE(SUBSTRING(JobID, 5, 8), '%Y%m%d'),
seq = SUBSTRING_INDEX(JobID, '-', -1)
;
Set up the AUTO_INCREMENT:
ALTER TABLE jobs
DROP PRIMARY KEY,
DROP JobID,
MODIFY seq SMALLINT(3) UNSIGNED NOT NULL AUTO_INCREMENT,
ADD PRIMARY KEY(initials, date, seq)
;
You can then recreate your JobID as required on SELECT (or even create a view from such a query):
SELECT CONCAT_WS(
'-',
initials,
DATE_FORMAT(date, '%Y%m%d'),
LPAD(seq, 3, '0')
) AS JobID,
-- etc.
If you're using InnoDB, whilst you can't generate sequence numbers in this fashion I'd still recommend normalising your data as above.

Answer 3

So, I found a query that works (thus far).
Declare maxjobID VARCHAR(16);
Declare jobincrement SMALLINT;
SET maxjobID =
(Select MAX(
ifnull(SUBSTRING(
(Select JobID FROM jobs WHERE SUBSTRING(JobID,5,8)=date_format(curdate(), '%Y%m%d')),
5,
12),0)
)
);
if maxjobID=0
then set jobincrement=1;
else set jobincrement=(select substring(maxjobID,10,3))+1;
end if;
Set NEW.JobID=concat
(New.AssignedCompany,'-',date_format(curdate(), '%Y%m%d'),'-',(select lpad(jobincrement,3,'0')));
Thanks for the responses! Especially eggyal for pointing out the auto_increment capabilities in MyISAM.