Mysql query from two tables as parent and child objects - mysql

Question

I am creating an Angularjs app with two tables "Contact Group" and "Contact List". The contact list table items have corespondent id to items in the contact group.
What I want to achieve is a MySQL/Sqlite select query that will have each contact list items as a child object of its parent.
contact_group
id | title
------------
1 | friends
2 | mates
3 | family
contact_list
id | gID | name | number
--------------------------
1 | 1 | dave |0208500
2 | 1 | dan |4213839
3 | 1 | sans |5656434
4 | 2 | fola |1918982
5 | 3 | brian|2398343
6 | 5 | grace|0934232
Select query results examples (this is what i want to get)
id: 1
title: friends
child: {id:1, name:dave, number:0208500}, {id:2, name:dan, number:4213839},{id:3, name:sans, number:5656434}
I case there is another way of doing it, this what i want to achieve. I have created an accordion with title from the contact_group title. Under each accordion are the correspondent contacts from the contact_list.
I will be glad if anyone can help me. Thank you

Answer 1

In order to achieve this you will have to use MySql GROUP_CONCAT (documentation here: https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat)
Using GROUP_CONCAT we will be able to join all matching rows from the contacts TB into a string in one column. With some more formatting of the text we glue together from the contacts TB and additional usage of CONCAT we will build the string in this column as a JSON string that you will then be able to work with on your application.
Here is the SQL:
SELECT
a.id,
a.title,
CONCAT(
'[',
GROUP_CONCAT(
CONCAT(
'{"id":',
b.id,
', "name":"',
b. `name`,
'", "number":"',
b.number,
'"}'
)
ORDER BY
b.`name`
), ']')
AS people
FROM
contact_group AS a
LEFT JOIN contact_list AS b ON a.id = b.gID
GROUP BY
a.id,
a.title
And this is the result we will get:
Don't forget to add Indexes and Foreign keys to your tables so query processing would be better.
SQLLITE Version:
in order to adjust the query to sqllite, there are 2 features that need to be changed.
SqlLite uses || operator instead of CONCAT and it does not support ORDER BY inside the GROUP_CONCAT. so for the SQLLITE DB the query will look like this:
SELECT
a.id,
a.title,
'[' ||
GROUP_CONCAT(
'{"id":' ||
b.id ||
', "name":"' ||
b. `name` ||
'", "number":"' ||
b.number ||
'"}'
) || ']'
AS people
FROM
contact_group AS a
LEFT JOIN contact_list AS b ON a.id = b.gID
GROUP BY
a.id,
a.title
MySQL Fiddle Demo
SqlLite Fiddle Demo

Answer 2

Try the below query,
select * from contact_group join contact_list on contact_group.id= contact_list.gid