How to do left join twice in one query? - sql

Question

How to do left join twice or other way to get data in result list like below in one query ?
I want media_information under media
{
id: 9,
gallery_id: 25,
media_id: 9,
media: {
id: 9,
media_information: {
id: 9,
media_id: 9,
}
},
}
query I tried
var dbQuery = `SELECT
gm.*,
row_to_json(m.*) as media,
row_to_json(mi.*) as media_information
FROM "gallery_media" gm
LEFT JOIN media m ON gm.media_id = m.id
LEFT JOIN media_information mi ON gm.media_id = mi.media_id
WHERE "gallery_id" = $1
ORDER BY gm.create_date DESC OFFSET $2 LIMIT $3`;
result
{
id: 9,
gallery_id: 25,
media_id: 9,
media: {
id: 9,
},
media_information: {
id: 9,
media_id: 9,
}
}
UPDATE
I also tried change ON m.id = mi.media_id but result nothing change
var dbQuery = `SELECT
gm.*,
row_to_json(m.*) as media,
row_to_json(mi.*) as media_information
FROM "gallery_media" gm
LEFT JOIN media m ON gm.media_id = m.id
LEFT JOIN media_information mi ON m.id = mi.media_id
WHERE "gallery_id" = $1
ORDER BY gm.create_date DESC OFFSET $2 LIMIT $3`;
table
CREATE TABLE IF NOT EXISTS "gallery_media"(
"id" SERIAL NOT NULL,
"gallery_id" integer NOT NULL,
"media_id" integer NOT NULL,
PRIMARY KEY ("id")
);
CREATE TABLE IF NOT EXISTS "media"(
"id" SERIAL NOT NULL,
PRIMARY KEY ("id")
);
CREATE TABLE IF NOT EXISTS "media_information"(
"id" SERIAL NOT NULL,
"media_id" integer NOT NULL,
PRIMARY KEY ("id") );
http://sqlfiddle.com/#!15/ff805

Answer 1

I think this is what you're after:
var dbQuery = `SELECT
gm.*,
row_to_json(m.*) as media,
row_to_json(mi.*) as media_information
FROM "gallery_media" gm
LEFT JOIN media m ON gm.media_id = m.id
LEFT JOIN media_information mi ON m.id = mi.media_id
WHERE "gallery_id" = $1
ORDER BY gm.create_date DESC OFFSET $2 LIMIT $3`;
ie: doing your second LEFT JOIN on media instead of gallery_media