Oracle How to assign usernames - sql

Question

How would I assign usernames for students using their initials followed by numbers that increment? I'm not sure how many students I have in my database and I would like their usernames to look like so "AC001, JD003 for example. And also, If the have similar initials I would like the username to continue incrementing in that order. For example "AC001" and "AC002"

Answer 1

You will need to use a trigger on BEFORE INSERT event and a sequence to implement this.
I will assume your table is as follows:
TABLE user
( userid VARCHAR2(100) -- PRIMARY KEY COLUMN
, firstname VARCHAR2(100)
, lastname VARCHAR2(100)
, .... -- Other columns
);
Create a sequence as follows:
CREATE SEQUENCE sq_userid;
You insert rows with userid column set to null.
INSERT INTO user VALUES (null, 'Jack', 'Daniels', ....);
Then, your trigger should look like this:
CREATE OR REPLACE TRIGGER trg_user
BEFORE INSERT ON user
REFERENCING new AS new old AS old
FOR EACH ROW
BEGIN
IF :new.userid IS NULL THEN
:new.userid := UPPER(LEFT(firstname, 1))
|| UPPER(LEFT(lastname, 1))
|| TO_CHAR(sq_userid.nextval, '099');
END IF;
END;
/
The trigger will put 'JD001' AS the value for userid in this instance.
For more information- Coding triggers, sequences and to_char.

Answer 2

i think this will also work
1st Create sequence user_seq;
insert into user values('user_name'||user_seq.nextval);
you can modify above query as per your requirement.

Answer 3

I fiddled a solution, but it's in MySQL. I'm sure you can get the general idea and convert it into Oracle (there's an Oracle 11g option in SQL Fiddle itself): http://sqlfiddle.com/#!2/e8ed5/1
Schema:
CREATE TABLE ALPHA_ROLL (
ALPHA1 CHAR(1),
ALPHA2 CHAR(1),
ROLL INTEGER,
PRIMARY KEY(ALPHA1, ALPHA2)
)//
CREATE TABLE user (
USERID VARCHAR(5),
FIRSTNAME VARCHAR(100),
LASTNAME VARCHAR(100),
PRIMARY KEY (USERID)
)//
CREATE TRIGGER trg_user
BEFORE INSERT ON user
FOR EACH ROW
BEGIN
SET #gen_user_id =
(SELECT CONCAT(ALPHA1,ALPHA2,LPAD((ROLL+1), 3, '0'))
FROM ALPHA_ROLL
WHERE ALPHA1 = UPPER(LEFT(NEW.firstname, 1))
AND ALPHA2 = UPPER(LEFT(NEW.lastname, 1))
LIMIT 1);
IF (#gen_user_id IS NULL) THEN
INSERT INTO ALPHA_ROLL (ALPHA1, ALPHA2, ROLL)
VALUES (UPPER(LEFT(new.firstname, 1)), UPPER(LEFT(new.lastname, 1)), 1);
SET #GEN_USER_ID =
CONCAT(UPPER(LEFT(new.firstname, 1)),
UPPER(LEFT(new.lastname, 1)),
'001');
ELSE
UPDATE ALPHA_ROLL SET ROLL = ROLL + 1
WHERE ALPHA1 = UPPER(LEFT(new.firstname, 1))
AND ALPHA2 = UPPER(LEFT(new.lastname, 1));
END IF;
SET new.userid = #GEN_USER_ID;
END//
SQL:
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Johnnie', 'Walker');
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Jason', 'Mraz');
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Mariah', 'Carrie');
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Justin', 'Morg');
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Matthew', 'Congoman');
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Jack', 'Waltson');
INSERT INTO USER (FIRSTNAME, LASTNAME) VALUES ('Jojo', 'Wonderful');
SELECT * FROM USER;
SELECT * FROM ALPHA_ROLL;
Result:
USERID FIRSTNAME LASTNAME
JM001 Jason Mraz
JM002 Justin Morg
JW001 Johnnie Walker
JW002 Jack Waltson
JW003 Jojo Wonderful
MC001 Mariah Carrie
MC002 Matthew Congoman
ALPHA1 ALPHA2 ROLL
J M 2
J W 3
M C 2