SELECT update_date, user_id, news_id,count(*) AS counter FROM t_commentWHERE user_id = 2AND news_id = 15GROUP BY user_id, news_id我想表示出來 MYSQL應該怎么寫 謝謝update_date user_id news_id counter2008-03-08 2 15 0 （此處顯示0）
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青春有我
TA貢獻1784條經驗 獲得超8個贊
SELECT
a.update_date,
a.user_id,
a.news_id,
(CASE WHEN b.counter IS NULL THEN 0 ELSE b.counter END) as 'Counter'
FROM (
SELECT update_date, user_id, news_id
FROM t_comment
GROUP BY update_date, user_id, news_id) a
LEFT OUTER JOIN
(
SELECT update_date, user_id, news_id,
count(*) AS counter FROM t_comment
WHERE user_id = 2 AND news_id = 15
GROUP BY user_id, news_id
) b
ON a.update_date = b.update_date
AND a.user_id = b.user_id
AND a.news_id = b.news_id
GO
T-SQL實現，原理如上，未經測試。
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