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");