how to group data entries with same id into a single entry? - mysql

Question

I am a beginner in MySQL as well as Typeorm. So my query returns data with the same ID like:
[
{
id: "1",
name: "john",
place: "San Francisco"
},
{
id: "1",
name: "john",
place: "Mumbai"
}
]
Now I want data where there is an entry with a unique id, let's say:
[
{
id: "1",
name: "john",
place: ["San Francisco", "Mumbai"]
}
]
can someone help me, how do I groupBy to achieve this result?

Answer 1

I doubt that you can get an array, but you could use group_concat.
https://mariadb.com/kb/en/group_concat/
The query would be something like
SELECT `id`, group_concat(`name`), group_concat(`place`) FROM <table_name> GROUP BY `id`
if the name doesn't need to be concatenated
SELECT `id`, `name`, group_concat(`place`) FROM <table_name> GROUP BY `id`
And then in your code you can split that string in array. Either use ',' which I think it's the default separator or use a custom one like '!#$!'

Answer 2

With MySQL you can use GROUP_CONCAT:
SELECT
id, name, GROUP_CONCAT(place)
FROM
<table_name>
GROUP BY
id
With TypeScript you can use Array.prototype.reduce():
const data = [{id: "1",name: "john",place: "San Francisco"},{id: "1",name: "john",place: "Mumbai"}]
const dataHash = data.reduce((a, { id, name, place }) => {
a[id] = a[id] || { id, name, place: [] }
a[id].place.push(place)
return a
}, {})
const result = Object.values(dataHash)
console.log(result)