Left join with multiple tables and conditions - mysql

Question

I want to sort after a value in another table the current table is referenced to. My query looks like this:
SELECT o._id,
o.titel,
o.beschreibung
FROM `objekt` AS o,
`objekt_einzel` AS oe,
`objekt_einzel_immobilie` AS oei,
`objekt_art` AS oa,
`verortung` AS v
#here
,`person` AS p,
`person_bauträger` AS pb
#end
WHERE o._id = oe.objekt_id
AND oe._id = oei.objekt_einzel_id
AND oa._id = o.objekt_art_id
AND o.ort_id = v._id
#here
AND oe.bauträger_id = pb._id
AND pb.person_id = p._id
#end
AND ( oei.justimmo_objekt_id = "0"
OR oei.justimmo_objekt_id IS NULL
OR oei.justimmo_objekt_id = "" )
#here
ORDER BY p.firmenbezeichnung ASC
The query is working fine but it shows me only values if oe.bauträger_id is set. I also want the null values. So I need a left join. I tried different things but I only get messages like unknown column or I get too much results.
I tried to simplify it to this:
SELECT o._id,
o.titel,
o.beschreibung
FROM `objekt` AS o,
`objekt_einzel` AS oe,
(SELECT oe.bauträger_id
FROM objekt o, objekt_einzel oe, objekt_einzel_immobilie oei
WHERE o._id = oe.objekt_id AND oe._id = oei.objekt_einzel_id) AS menge1
LEFT JOIN
(SELECT pb._id AS bauträger_id
FROM person p, person_bauträger pb
WHERE p._id = pb.person_id) AS menge2
ON menge1.bauträger_id = menge2.bauträger_id
WHERE o._id = oe.objekt_id AND oe.bauträger_id = menge1.bauträger_id
but here I get a too big result set. I don't know how to explain this better. The data sets are too big to create an example. I hope you understand what I mean.

Answer 1

SELECT o._id,
o.titel,
o.beschreibung
FROM `objekt` AS o
JOIN `objekt_einzel` AS oe ON o._id = oe.objekt_id
JOIN `objekt_einzel_immobilie` AS oei ON oe._id = oei.objekt_einzel_id
JOIN `objekt_art` AS oa ON o.objekt_art_id = oa._id
JOIN `verortung` AS v ON o.ort_id = v._id
LEFT JOIN `person_bauträger` AS pb ON oe.bauträger_id = pb._id
LEFT JOIN `person` AS p ON pb.person_id = p._id
WHERE oei.justimmo_objekt_id = "0"
OR oei.justimmo_objekt_id IS NULL
OR oei.justimmo_objekt_id = ""
ORDER BY p.firmenbezeichnung ASC
This second try should work as it is just the original code rewritten using JOIN syntax and with LEFT JOINs.