Mysql join on multiple columns - php

Question

I am having an issue where I want to join several columns by an id.
My first table looks like this:
submitter_id reviewer_id processor_id
75 34 91
The table that I want to join looks like this:
id first_name last_name
75 Bob Smith
34 Albert McDonald
91 Joe Blo
I am trying to create a query that will look at each id in my first table and then get the first and last name's for each id.
For example, a query that does this should return something like:
[
75 => "Bob Smith",
34 => "Albert McDonald",
91 => "Joe Blo"
];
Can anybody help me construct a query that can accomplish this? Thanks!

Answer 1

Join the same table 3 times with different alias names
select t1.submitter_id, t1.reviewer_id, t1.processor_id,
t2.first_name as submitter_firstname, t2.last_name as submitter_lastname,
t3.first_name as reviewer_firstname, t3.last_name as reviewer_lastname,
t4.first_name as processor_firstname, t4.last_name as processor_lastname
from firstTable t1
left join namesTable t2 on t1.submitter_id = t2.id
left join namesTable t3 on t1.reviewer_id = t3.id
left join namesTable t4 on t1.processor_id = t4.id

Answer 2

I think what your actually looking for is more like this:
SELECT n.id, CONCAT(n.first_name, ' ', n.last_name)
FROM names n
JOIN ids i
ON n.id = i.submitter_id
OR n.id = i.reviewer_id
OR n.id = i.processor_id
GROUP BY n.id;
This is only doing one join, shows the records with the 2 columns you actually want and restricts so users are only listed 1 time. Also since you probably don't want to return just the ID if the user doesn't have a name setup you don't want a left join.
Edit:
If you need indexes you can make one on submitter_id, reviewer_id, processor_id if the performance is needed for you.

Answer 3

You want all in one resultset, so you could use UNION ALL:
SELECT p.id, CONCAT(p.first_name, ' ', p.last_name) as name
FROM person p
JOIN firstTable f
ON p.id = f.submitter_id
UNION ALL
SELECT p.id, CONCAT(p.first_name, ' ', p.last_name) as name
FROM person p
JOIN firstTable f
ON p.id = f.reviewer_id
UNION ALL
SELECT p.id, CONCAT(p.first_name, ' ', p.last_name) as name
FROM person p
JOIN firstTable f
ON p.id = f.processor_id
I think this is a better approach if you plan to use some conditions only for some group, like where reviewer_id > 100. If not, the Sir. Egole is cleaner.

Answer 4

Assuming that you need one row in the first table to return one row at the result.
SELECT tt.submitter_id , CONCAT(ta.first_name, ' ', ta.last_name) ,
tt.reviewer_id , CONCAT(tb.first_name, ' ', tb.last_name) ,
tt.processor_id , CONCAT(tc.first_name, ' ', tc.last_name)
FROM `transaction` as tt , `names` as ta , `names` as tb , `names` as tc
WHERE tt.submitter_id = ta.id AND
tt.reviewer_id = tb.id AND
tt.processor_id = tc.id
The result would be the 3 ids with the corresponding names in one row per transaction.