无法从其他表中获取 2 个值 SQL 查询，

Question

I'm newbie on SQL, I have 2 simple tables

ip_track

id	current_ip_id	old_ip_id
1	1	1
2	2	9
3	1	8

And ip

id	ip
1	8.8.8.8
2	195.19.97.117
8	8.8.4.4
9	1.2.3.4

AND I want to get current_ip_id and old_ip_id with its ip in SELECT Statement like

id	current_ip_id	current_ip	old_ip_id	old_ip
1	1	8.8.8.8	1	8.8.8.8
2	2	195.19.97.117	9	1.2.3.4
3	1	8.8.8.8	8	8.8.4.4

But if ids are different I got duplicates For example, for
SELECT ip_track.id, current_ip_id, ip AS current_ip, old_ip_id, ip AS old_ip FROM ip_track INNER JOIN ip ON current_ip_id = ip.id OR old_ip_id = ip.id

id	current_ip_id	current_ip	old_ip_id	old_ip
1	1	8.8.8.8	1	8.8.8.8
2	2	195.19.97.117	9	195.19.97.117
3	2	1.2.3.4	9	1.2.3.4
4	1	8.8.8.8	8	8.8.8.8
5	1	8.8.4.4	8	8.8.4.4

But expect

id	current_ip_id	current_ip	old_ip_id	old_ip
1	1	8.8.8.8	1	8.8.8.8
2	2	195.19.97.117	9	1.2.3.4
3	1	8.8.8.8	8	8.8.4.4

How can it be solved?

Answer 1

Join the ip table to the ip_track table twice :

SELECT
    ipt.id,
    ipt.current_ip_id,
    ip1.ip AS current_ip,
    ipt.old_ip_id,
    ip2.ip AS old_ip
FROM ip_track ipt
LEFT JOIN ip ip1
    ON ip1.id = ipt.current_ip_id
LEFT JOIN ip ip2
    ON ip2.id = ipt.old_ip_id
ORDER BY ipt.id;