MySQL INNER JOIN Multiple columns - mysql

Question

I have two tables
Table1: violations
Columns: date, time, pdid, pname, v1, v2, v3, v4
Each v1 through v4 has an integer value which corresponds to a single entry (ID) in table 2.
table2: parking_violations
columns: code, section, description, ID
I need to query each record of violations based on pdid, and match each 'v1-v4' to column 'ID' in the p_violations table.
SELECT
parking.date,
parking.time,
parking.pname,
parking_violations.code,
parking_violations.section,
parking_violations.description
FROM
parking
INNER JOIN parking_violations ON parking.v1=parking_violations.ID
WHERE
pdid=5
This returns the correct records for V1, but I cannot figure out how to also return V2-V4 all populated by matching the value to ID.

Answer 1

Like #fa06 explain, you can use multiple joins to the same table, but instead of inner join i will use left join, this way i have the flexibility of get rows where not all vN have matching IDs on the table parking_violations.
SELECT
parking.date,
parking.time,
parking.pname,
pv1.code,
pv1.section,
pv1.description,
pv2.code,
pv2.section,
pv2.description,
pv3.code,
pv3.section,
pv3.description,
pv4.code,
pv4.section,
pv4.description
FROM
parking
LEFT JOIN
parking_violations AS pv1 ON pv1.ID = parking.v1
LEFT JOIN
parking_violations AS pv2 ON pv2.ID = parking.v2
LEFT JOIN
parking_violations AS pv3 ON pv3.ID = parking.v3
LEFT JOIN
parking_violations AS pv4 ON pv4.ID = parking.v4
WHERE
parking.pdid = 5;

Answer 2

use join multiple time with alias like below:
SELECT
parking.date,
parking.time,
parking.pname,
parking_violations.code,
parking_violations.section,
parking_violations.description
FROM
parking
INNER JOIN parking_violations ON parking.v1=parking_violations.ID
inner join parking_violations a ON parking.v2=a.ID
inner join parking_violations b ON parking.v3=b.ID
inner join parking_violations c ON parking.v4=d.ID
WHERE
pdid=5