在 mysql 中在一列中合并多行？ 当具有不同值的相同 ID 时

Question

i have a query in which getting 2 record of same id but different groups(column) value. here is the query:

SELECT rule.id, rule.rule_name,group_rule.groupName
  FROM rule LEFT JOIN rule_groups ON rule.id=rule_groups.rule_id
  LEFT JOIN group_rule ON   rule_groups.group_rule_id=group_rule.id

result: ---------------------------------

|id     |rule_name   | groupName
|1      |A           | app
|1      |A           |jaz

now want to combine these two rows in one record. how to modify query to get expected result.

expected:

|id     |rule_name   | groupName
|1      |A           | app, jaz




 

Answer 1

I think you just want group_concat() :

select r.id, r.rule_name, group_concat(gr.groupName separator ', ')
from rule r left join
     rule_groups rg
     on r.id = rg.rule_id left join
     group_rule gr
     on rg.group_rule_id = gr.id
group by r.id, r.rule_name;

Note that I also introduced table aliases so the query is easier to write and read.