求mysql一條語句,該如何處理

求mysql一條語句
按id降序查詢幾種情況的各一條記錄，用一條語句能否實現？

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union 可不可以的，沒用過
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對

(select * from a order by id desc limit 0,1) union all (select * from b order by id desc order by id desc limit 0,1)
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可以啊，用UNION ALL
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按情況分組 每組取一條記錄

SQL code

SELECT * FROM (SELECT * FROM `table` ORDER BY `condition` DESC) t GROUP BY `condition`;
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