My MySQL database contains two tables: user
and coupon
(one-to-one relationship).
I would like to select all users that do not have a coupon and create a new one (random and unique).
user TABLE:
___________________________________
| id | name | coupon_id |
-----------------------------------
1 John 5
2 Mary (null) // Need to create one coupon.
3 Doe 2
4 Max (null) // Need to create one coupon.
5 Rex 1
7 Bill (null) // Need to create one coupon.
coupon TABLE:
______________________________________________
| id | code (random 6-chars - unique) |
----------------------------------------------
1 80k2ni
2 0akdne
5 nk03jd
Shortcuts:
Select all users without coupon: SELECT * from user WHERE coupon_id IS NULL;
Generate a random 6-chars string (MySQL): LEFT(sha1(rand()), 6)
.
Assuming you don't mind continuing upwards from 6 for the next coupon_id
, this can be done as follows (see SQL Fiddle Demo ):
-- Declare and set variables
SET @id_for_insert = (SELECT MAX(`id`) FROM `coupon`);
SET @id_for_update = @id_for_insert;
-- Insert new coupons
INSERT INTO `coupon` (id, code)
SELECT @id_for_insert := @id_for_insert + 1, LEFT(SHA1(RAND()), 6)
FROM `user`
WHERE coupon_id IS NULL;
-- Update users that don't already have a coupon with the newly created coupons
UPDATE `user`
SET coupon_id = @id_for_update := @id_for_update + 1
WHERE coupon_id IS NULL;
Something like this maybe:
Insert into coupon
select distinct id,LEFT(sha1(rand()), 6)
from user WHERE coupon_id IS NULL
After this, you can update coupon in user table using simple update with join.
//check if works inform me i will be glad
CREATE PROCEDURE `syncCouponUser` ()
BEGIN
INSERT INTO coupon(id,code)//create coupons var no-used user ids
select
id,
LEFT(sha1(rand())
from user
where coupon_id IS NULL ;
UPDATE user //add coupons from coupon table with matches
SET coupon_id=(
select c.coupon_id
from coupon c join user u
on c.id=u.id);
END
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