[英]Left join with multiple tables and conditions
我想對當前表所引用的另一個表中的值進行排序。 我的查詢如下所示:
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
查詢工作正常,但它表明我只值如果oe.bauträger_id
設置。 我也想要null
值。 所以我需要左聯接。 我嘗試了不同的方法,但只收到諸如unknown column
類的消息,或者得到了太多結果。
我試圖簡化為:
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
但是在這里我得到了太大的結果集。 我不知道如何更好地解釋這一點。 數據集太大,無法創建示例。 我希望你明白我的意思。
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
第二次嘗試應該起作用,因為它只是使用JOIN語法和LEFT JOINs重寫的原始代碼。
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