更新行而不删除mysql中的先前值

Question

One of my table has a field user_ids and the value of the field like 2,3

group_id| user_ids  
--------|------------   
1       | 2,3  
--------|------------  
2       | 5,8

I want to update the field without deleting the current value. For ex. If I need to add 5 for group_id id 1, then 2,3 should be like 2,3,5

I m using this query:

UPDATE users_group SET user_ids = CONCAT( SUBSTRING( user_ids, 1, CHAR_LENGTH( user_ids ) -1 ) , ',5' ) WHERE group_id =1

But it is deleting previous value with comma.

group_id| user_ids  
--------|------------   
1       | ,5  
--------|------------  
2       | 5,8

can anyone suggest the right way for this?

Answer 1

Can you not just concatenate it on, rather than trying to split it up first?

UPDATE users_group 
SET user_ids = CONCAT_WS(',', user_ids, '5' ) 
WHERE group_id =1

But this does suggest a badly normalised database design. Generally a comma separated list should instead be stored as rows on another table (ie, one row per value in the list) as suggested by Mark Baker.

EDIT - If you want to only have a single copy of any id in each user_ids field, irrespective of how many times you try to insert it, and you want to be able to add multiple ids at once:-

UPDATE users_group a
INNER JOIN
(
    SELECT 3 AS an_id
    UNION 
    SELECT 4
) b
ON FIND_IN_SET(b.an_id, a.user_ids) = 0
SET a.user_ids = CONCAT_WS(',', a.user_ids, b.an_id ) 
WHERE a.group_id =1

EDIT again - if you have a table of users containing the ids then you can select the ids from that where the id is one of those you want to add.

Something like this.

UPDATE users_group a
INNER JOIN
(
    SELECT id
    FROM users
    WHERE id IN (3, 4)
) b
ON FIND_IN_SET(b.id, a.user_ids) = 0
SET a.user_ids = CONCAT_WS(',', a.user_ids, b.id ) 
WHERE a.group_id =1

Answer 2

update table1 set name = concat(name, ', ', 5) WHERE group_id =1

Answer 3

Please try this query. It may be useful for you.

UPDATE users_group SET user_ids = CONCAT( user_ids , ',5' ) WHERE group_id =1

Answer 4

Try the below query:

UPDATE users_group 
SET user_ids = CONCAT( user_ids , ',5' ) 
WHERE group_id =1