MySQL one to many get the no matching record - mysql

Question

Im not good at explaining things so please bear with me.. Here's what I'm trying to do. I want to get the result of rows with no matching record to the table(tbl_personnel_documents) if I'm looking for the documents with a "YES" priority and based on their position.
Here's the structure of the table for employee:
tbl_personnel_info
id name position_id
1 John 1
2 Sharyn 2
3 Stacie 4
4 Kevin 3
5 Cristine 3
Table for Position:
tbl_position
id position_name
1 IT Manager
2 Accounting Staff
3 IT Staff
4 H.R Manager
5 Admin Staff
Table for personnel documents:
tbl_personnel_documents
id personnel_id document_id document_num
1 1 3 111-222-333-444
2 1 4 AB-CC-DD
3 2 1 CC-BB-DD
4 4 2 1-2-3-4-5
5 3 4 C1-D2-X1-D2-G3
Table for documents name
tbl_documents
id document_name priority
1 Passport YES
2 ROPC NO
3 US Visa YES
4 AUS Visa YES
Table for document priority based on their position
tbl_priority_docs_per_position
id position_id document_id
1 1 1
2 1 3
3 1 4
In this case, John's position is an IT Manager which have no record of passport in the table(tbl_personnel_documents). And since the document Passport is a priority document for IT Manager but it is missing, it must display the result.
Im currently stuck in here.. I can't get the desired result.. Here's my code:
SELECT td.document_name
FROM tbl_personnel_info AS tpi
LEFT JOIN tbl_position AS tp
ON tp.id = tpi.position_id
LEFT JOIN tbl_personnel_documents AS tpd
ON tpi.id = tpd.personnel_id
LEFT JOIN tbl_documents AS td
ON td.id = tpd.document_id
LEFT JOIN tbl_priority_docs_per_position AS tpriority
ON tpriority.position_id = tpi.position_id AND tpriority.document_id = tpd.document_id
WHERE td.priority = 'YES'
AND tpi.id = 1 -- John's ID
AND tpriority.document_id IS NULL
Please help.. Thank you
Update: I manage to partially get the result with this code:
SELECT td.document_name
FROM tbl_personnel_info AS tpi
LEFT JOIN tbl_position AS tp
ON tp.id = tpi.position_id
LEFT JOIN tbl_personnel_documents AS tpd
ON tpi.id = tpd.personnel_id
LEFT JOIN tbl_documents AS td
ON td.priority = 'YES'
LEFT JOIN tbl_priority_docs_per_position AS tpriority
ON tpriority.position_id = tpi.position_id AND tpriority.document_id = tpd.document_id
WHERE tpi.id = 1 -- John's ID
AND tpriority.document_id IS NULL
GROUP BY td.id
Now my problem is whenever I change the position_id of tbl_priority_docs_per_position, I still get the same result.

Answer 1

When you use a left join you must be very careful how you reference that table in the where clause or you might override the join. Here however I believe it is the sequence of joins:
SELECT
*
FROM tbl_personnel_info AS tpi
INNER JOIN tbl_position AS tp ON tp.id = tpi.position_id
INNER JOIN tbl_priority_docs_per_position AS tpriority ON tpriority.position_id = tpi.position_id
LEFT JOIN tbl_personnel_documents AS tpd ON tpi.id = tpd.personnel_id
AND tpriority.document_id = tpd.document_id
LEFT JOIN tbl_documents AS td ON td.id = tpd.document_id
WHERE tpi.id = 1 -- John's ID
AND td.priority IS NULL
;
Demo
| id | name | position_id | id | position_name | id | position_id | document_id | id | personnel_id | document_id | document_num | id | document_name | priority |
|----|------|-------------|----|---------------|----|-------------|-------------|--------|--------------|-------------|--------------|--------|---------------|----------|
| 1 | John | 1 | 1 | IT Manager | 1 | 1 | 1 | (null) | (null) | (null) | (null) | (null) | (null) | (null) |