使用JOIN查詢從數據庫中選擇上次時間戳

Question

我有一個查詢來選擇組和組發佈。在發佈表中有一個時間戳列表和一個group_id。我需要在帖子表中選擇與組ID相關聯的最大時間戳。

這裏是我的查詢

$query = " 
    SELECT groups.group_name, groups.group_info, groups.group_tags, postings.timestamp 
    FROM groups 
    LEFT JOIN postings ON groups.group_id = postings.group_id 
    GROUP BY groups.group_id 
    ORDER BY `postings`.`timestamp` DESC 
"; 

Answer 1

$query = " 
    SELECT groups.group_name, groups.group_info, groups.group_tags, max(postings.timestamp) 
    FROM groups 
    LEFT JOIN postings ON groups.group_id = postings.group_id 
    GROUP BY groups.group_id 
    ORDER BY `postings`.`timestamp` DESC 
";