Same Join Constraints on Multiple Columns - mysql

Question

We have a situation that I have been able to recreate with the following simple example. I have the following two sample tables:
CREATE TABLE contact_info
(
id INT UNSIGNED AUTO_INCREMENT,
priContactId INT,
secContactId INT,
blahBlah VARCHAR(32),
PRIMARY KEY(id)
);
and
CREATE TABLE name_lookup
(
id INT UNSIGNED AUTO_INCREMENT,
contactID INT,
contactName VARCHAR(32),
PRIMARY KEY(id)
);
I populate them as follows:
INSERT INTO contact_info(priContactId, secContactId, blahBlah) VALUES(1, 3, "Team A"), (4, 2, "Team B");
INSERT INTO name_lookup(contactID, contactName) VALUES(1, "John Doe"), (2, "Mary Smith"), (3, "Jose Garcia"), (4, "Larry Brown");
Obviously, the contents of the tables are as follows:
+----+--------------+--------------+----------+
| id | priContactId | secContactId | blahBlah |
+----+--------------+--------------+----------+
| 1 | 1 | 3 | Team A |
| 2 | 4 | 2 | Team B |
+----+--------------+--------------+----------+
+----+-----------+-------------+
| id | contactID | contactName |
+----+-----------+-------------+
| 1 | 1 | John Doe |
| 2 | 2 | Mary Smith |
| 3 | 3 | Jose Garcia |
| 4 | 4 | Larry Brown |
+----+-----------+-------------+
We would like to perform a JOIN operation so that we get output like this:
+-------------+-------------+--------+
| John Doe | Jose Garcia | Team A |
+-------------+-------------+--------+
| Larry Brown | Mary Smith | Team B |
+-------------+-------------+--------+
The join constraints for both the priContactId and secContactId columns are the same and I am having tough time figuring out what the JOIN query should look like.
FYI, we are using MySQL version 5.6.49.

Answer 1

Two separate columns needs 2 separate table copies join.
SELECT t1.contactName name1, t2.contactName name1, t3.blahBlah team
FROM name_lookup t1
JOIN name_lookup t2
JOIN contact_info t3 ON t1.contactID = t3.priContactId
AND t2.contactID = t3.secContactId

Answer 2

This would normally be handled with two joins. You don't have not null constraints on the two contacts, so I would suggest outer joins:
select nl_pri.contactName as PrimaryName, nl_sec.contactName as SecondaryName,
ci.blahblah
from contact_info ci left join
name_lookup nl_pri
on ci.priContactId = nl_pri.contactId left join
name_lookup nl_sec
on c.secContactId = nl_sec.contactId;
Notes:
The left join keeps all contacts, even those that don't have both primary and secondary.
Table aliases make the query easier to write and read. The table aliases should be meaningful.
You should define the foreign key relationships, so it is clear that the contact ids refer to the name_lookup table.