Question

select * from generic_shop 
    where (type, timestamp) in (
        select  type, max(timestamp) 
            from generic_shop 
            group by type
    ) order by type

如果在命令行中进行了测试，则此查询有效，但在某个房间中它声称where (type, timestamp)处有错误。我如何重写它以使其正常工作？预先感谢。

Answer 1

SQLite不支持涉及左侧多列的IN子句。但是，您的查询很容易使用其他方式表示：

SELECT g1.*
FROM generic_shop g1
INNER JOIN
(
    SELECT type, MAX(timestamp) AS max_timestamp
    FROM generic_shop
    GROUP BY type
) g2
    ON g1.type = g2.type AND g1.timestamp = g2.max_timestamp;
ORDER BY
    g1.type;

Room db多列子查询

1 个答案: