Programmatically increasing the count of a unique column [duplicate] - php

Question

I have table like this
table
id Varchar(45) NOT NULL AUTO_INCREMENT PRIMARY KEY,
name CHAR(30) NOT NULL,
I want to increment my id field like 'LHPL001','LHPL002','LHPL003'... etc.
What should I have to do for that? Please let me know any possible way.

Answer 1

If you really need this you can achieve your goal with help of separate table for sequencing (if you don't mind) and a trigger.
Tables
CREATE TABLE table1_seq
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
);
CREATE TABLE table1
(
id VARCHAR(7) NOT NULL PRIMARY KEY DEFAULT '0', name VARCHAR(30)
);
Now the trigger
DELIMITER $$
CREATE TRIGGER tg_table1_insert
BEFORE INSERT ON table1
FOR EACH ROW
BEGIN
INSERT INTO table1_seq VALUES (NULL);
SET NEW.id = CONCAT('LHPL', LPAD(LAST_INSERT_ID(), 3, '0'));
END$$
DELIMITER ;
Then you just insert rows to table1
INSERT INTO Table1 (name)
VALUES ('Jhon'), ('Mark');
And you'll have
| ID | NAME |
------------------
| LHPL001 | Jhon |
| LHPL002 | Mark |
Here is SQLFiddle demo

Answer 2

Create a table with a normal numeric auto_increment ID, but either define it with ZEROFILL, or use LPAD to add zeroes when selecting. Then CONCAT the values to get your intended behavior. Example #1:
create table so (
id int(3) unsigned zerofill not null auto_increment primary key,
name varchar(30) not null
);
insert into so set name = 'John';
insert into so set name = 'Mark';
select concat('LHPL', id) as id, name from so;
+---------+------+
| id | name |
+---------+------+
| LHPL001 | John |
| LHPL002 | Mark |
+---------+------+
Example #2:
create table so (
id int unsigned not null auto_increment primary key,
name varchar(30) not null
);
insert into so set name = 'John';
insert into so set name = 'Mark';
select concat('LHPL', LPAD(id, 3, 0)) as id, name from so;
+---------+------+
| id | name |
+---------+------+
| LHPL001 | John |
| LHPL002 | Mark |
+---------+------+

Answer 3

I know it is late but I just want to share on what I have done for this. I'm not allowed to add another table or trigger so I need to generate it in a single query upon insert. For your case, can you try this query.
CREATE TABLE YOURTABLE(
IDNUMBER VARCHAR(7) NOT NULL PRIMARY KEY,
ENAME VARCHAR(30) not null
);
Perform a select and use this select query and save to the parameter #IDNUMBER
(SELECT IFNULL
(CONCAT('LHPL',LPAD(
(SUBSTRING_INDEX
(MAX(`IDNUMBER`), 'LHPL',-1) + 1), 5, '0')), 'LHPL001')
AS 'IDNUMBER' FROM YOURTABLE ORDER BY `IDNUMBER` ASC)
And then Insert query will be :
INSERT INTO YOURTABLE(IDNUMBER, ENAME) VALUES
(#IDNUMBER, 'EMPLOYEE NAME');
The result will be the same as the other answer but the difference is, you will not need to create another table or trigger. I hope that I can help someone that have a same case as mine.

Answer 4

Here is PostgreSQL example without trigger if someone need it on PostgreSQL:
CREATE SEQUENCE messages_seq;
CREATE TABLE IF NOT EXISTS messages (
id CHAR(20) NOT NULL DEFAULT ('message_' || nextval('messages_seq')),
name CHAR(30) NOT NULL,
);
ALTER SEQUENCE messages_seq OWNED BY messages.id;