在 MySQL 的 Join 語句中查詢最大日期
要擷取 MySQL 中記錄的歷史位置，您可以使用 JOIN 語句。但是，當遇到效能問題和結果中存在重複資料時，需要修改方法。
修改查詢
只擷取每個記錄 ID的最新修改時間和位置，請考慮以下查詢：
SELECT t1.received_id
, t1.transaction_id
, t1.date_modified
, l.location
FROM transactions t1
JOIN ( SELECT received_id, MAX(date_modified) maxmodify FROM transactions GROUP BY received_id) max_record
ON max_record.received_id = t1.received_id
AND max_record.maxmodify = t1.date_modified
JOIN locations l
ON l.location_id = t1.location_id
JOIN received r
ON r.received_id = t1.received_id
WHERE t1.received_id = '1782'
ORDER
BY t1.date_modified DESCKey修改
修改位於子查詢：
SELECT received_id, MAX(date_modified) maxmodify FROM transactions GROUP BY received_id
此子查詢會檢索每個received_id的最大日期。
加入最大值
然後主查詢使用兩個連接到這個子查詢條件：
以上是如何使用JOIN語句有效率地查詢MySQL中最新的位置資料？的詳細內容。更多資訊請關注PHP中文網其他相關文章！
