[英]SQL GROUP BY multiple columns?
我有一張桌子,我需要按兩個不同的列對條目進行分組
這是我的代碼
SELECT *
FROM (
SELECT max(user_msg.id) AS mid, max(user_msg.timestamp) AS tsp, user_msg.text,
usr1.id AS u1_id, usr1.nickname AS u1_nickname, usr1.avatar AS u1_avatar, usr1.avatar_art AS u1_avatar_art,
usr2.id AS u2_id, usr2.nickname AS u2_nickname, usr2.avatar AS u2_avatar, usr2.avatar_art AS u2_avatar_art,
COUNT(user_msg.id) AS cnt
FROM user_msg
join user using (client_id)
LEFT JOIN user AS usr1 ON user_msg.from_id=usr1.id
LEFT JOIN user AS usr2 ON user_msg.to_id=usr2.id
WHERE user_msg.to_id = '".$user_id."' AND to_delete='0' OR user_msg.from_id = '".$user_id."' AND to_delete='0'
group by u1_id, u2_id ORDER by tsp DESC
) c
它應該類似於u1_id和u2_id的分組
您需要使用原始列名,而不是別名。 它們還沒有被處理(嗯,在SQL Server中還不是:不確定MYSQL)。
...
WHERE user_msg.to_id = '".$user_id."' AND to_delete='0' OR user_msg.from_id = '".$user_id."' AND to_delete='0'
group by usr1.id, usr2.id
ORDER by tsp DESC
...
因此,我懷疑GROUP BY是錯誤和模棱兩可的,需要像下面的標准SQL一樣。 有或沒有別名
像這個問題: SQL查詢未顯示預期結果
[結束編輯]
注意,要制作此標准SQL(或在其他任何RDBMS上運行),您需要使用GROUP BY中所有不在匯總中的列:
SELECT
max(user_msg.id) AS mid,
max(user_msg.timestamp) AS tsp,
user_msg.text,
usr1.id AS u1_id, usr1.nickname AS u1_nickname, usr1.avatar AS u1_avatar, usr1.avatar_art AS u1_avatar_art,
usr2.id AS u2_id, usr2.nickname AS u2_nickname, usr2.avatar AS u2_avatar, usr2.avatar_art AS u2_avatar_art,
COUNT(user_msg.id) AS cnt
FROM user_msg
join user using (client_id)
LEFT JOIN user AS usr1 ON user_msg.from_id=usr1.id
LEFT JOIN user AS usr2 ON user_msg.to_id=usr2.id
WHERE user_msg.to_id = '".$user_id."' AND to_delete='0' OR user_msg.from_id = '".$user_id."' AND to_delete='0'
GROUP BY
user_msg.text, usr1.id, usr1.nickname, usr1.avatar, usr2.avatar_art,
usr2.id, usr2.nickname, usr2.avatar, usr1.avatar_art
ORDER by tsp DESC
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