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geoffrey
geoffrey
28,736 Points
Posted by geoffrey
geoffrey
28,736 Points

Combine two SQL queries

Hi there, I'm working on a projet at the moment and I have difficulties to retrieve in one query all the needed datas from 3 differents tables.

I can get the datas I need using two differents queries, I tried to combine both of them using the UNION keyword in my query, but it doesn't seem to work.

Here is the two queries separated, giving the datas I need, the challenge for me is to combine both in one query, till now I haven't succeed hence this post..

SELECT b.ID_bug,b.date,b.author,b.app_url,b.app_version,
b.title,b.description,b.img,b.priority,b.last_action,
l.name AS label_name ,l.color AS label_color
FROM t_bugs b JOIN t_labels l ON FK_label_ID = ID_label
WHERE id_bug = 2 ;

SELECT  b.ID_bug,b.date,b.author,b.app_url,b.app_version,
b.title,b.description,b.img,b.priority,b.last_action,
d.pseudo FROM t_bugs b JOIN t_devs d ON FK_dev_ID =  ID_dev
WHERE id_bug = 2;

2 Answers

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

I think you just need to use a double join. join t_bugs and t_lables together. then join t_devs to that. 

SELECT 
b.ID_bug,b.date,b.author,b.app_url,b.app_version,
b.title,b.description,b.img,b.priority,b.last_action,
l.name AS label_name ,l.color AS label_color
FROM t_bugs b 
JOIN t_labels l ON FK_label_ID = ID_label
JOIN t_devs d ON FK_dev_ID =  ID_dev
WHERE id_bug = 2;
geoffrey
geoffrey
28,736 Points
geoffrey
geoffrey
28,736 Points

That was so simple, I was pretty sure once I I had done the first JOIN, I couldn't do another one... Thank you man :)

Cena Mayo
Cena Mayo
55,236 Points
Cena Mayo
Cena Mayo
55,236 Points

This StackOverflow article on querying multiple tables goes into a lot of detail about the difference between JOIN and UNION and when to use each.