Generate auto incremented id for BPM application - mysql

Question

Within a BPM web application, I have a field for an invoice # on a particular page but I need for it to be auto generated every time a user attaches an invoice and views that page. That number must be unique and preferably auto-incremented. A value for the invoice # field can be displayed by querying from a table from an external MYSQL database. So every time a user lands on that particular page, a SELECT query statement can be fired.
On MYSQL end, how would I set this up? So basically, I would like to setup a query for that invoice # field where it will for run a query for example,
SELECT invoice_num FROM invoice_generator
and every time this query runs, it would return the next incremented number.

Answer 1

You can use mysql trigger concept here....
I have added one example here...
It will be very usefull for u (see this link also :http://www.freemindsystems.com/mysql-triggers-a-practical-example/)
CREATE TABLE `products` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(50) NOT NULL DEFAULT '',
`price` int(20) NOT NULL DEFAULT '0',
`other` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `products_name_idx` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `freetags` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`tag` varchar(50) NOT NULL DEFAULT '',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `freetagged_objects` (
`tag_id` int(20) NOT NULL DEFAULT '0',
`object_id` int(20) NOT NULL DEFAULT '0',
`tagged_on` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`module` varchar(50) NOT NULL DEFAULT '',
PRIMARY KEY (`tag_id`, `object_id`),
KEY `freetagged_objects_tag_id_object_id_idx` (`tag_id`, `object_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
INSERT_PRODUCTS_TAGS
DELIMITER ||
DROP TRIGGER IF EXISTS insert_products_tags;
||
DELIMITER ##
CREATE TRIGGER insert_products_tags AFTER INSERT ON products
FOR EACH ROW
BEGIN
DECLARE current_id integer;
DECLARE tag_id integer;
DECLARE next integer;
DECLARE tag_field varchar(255);
DECLARE next_sep integer;
DECLARE current_tag varchar(255);
DECLARE right_tag varchar(255);
-- We use the field other as comma-separated tag_field
SET tag_field = NEW.other;
-- Check for empty tags
IF (CHAR_LENGTH(tag_field) <> 0) THEN
-- Loop until no more ocurrencies
set next = 1;
WHILE next = 1 DO
-- Find possition of the next ","
SELECT INSTR(tag_field, ',') INTO next_sep;
IF (next_sep > 0) THEN
SELECT SUBSTR(tag_field, 1, next_sep - 1) INTO current_tag;
SELECT SUBSTR(tag_field, next_sep + 1, CHAR_LENGTH(tag_field)) INTO right_tag;
set tag_field = right_tag;
ELSE
set next = 0;
set current_tag = tag_field;
END IF;
-- Drop spaces between comas
SELECT TRIM(current_tag) INTO current_tag;
-- Insert the tag if not already present
IF (NOT EXISTS (SELECT tag FROM freetags WHERE tag = current_tag)) THEN
-- Insert the tag
INSERT INTO freetags (tag) values (current_tag);
SELECT LAST_INSERT_ID() INTO tag_id;
ELSE
-- Or get the id
SELECT id FROM freetags WHERE tag = current_tag INTO tag_id;
END IF;
-- Link the object tagged with the tag
INSERT INTO freetagged_objects
(tag_id, object_id, module)
values
(tag_id, NEW.id, 'products');
END WHILE;
END IF;
END;
##
Now If you execute an insert on products table:
INSERT INTO PRODUCTS
(name, price, other)
values
("product1", 2, "tag1, tag2,tag3 , tag 4");