Question

我得到以下MySQL查询，我需要转换为SQLite查询（在我的Android应用程序中使用）

select *
from msgsList
where (least(msg_from, msg_to), greatest(msg_from, msg_to), msg_time)       
in 
(
    select 
       least(msg_from, msg_to) as x, greatest(msg_from, msg_to) as y, 
       max(msg_time) as msg_time
    from msgsList 
    group by x, y
);

Answer 1

在SQLite中，LEAST（）/ GREATEST（）只是被称为MIN（）/ MAX（）。

SQLite不支持使用元组的IN，但您可以将表连接到子查询：

SELECT msgsList.*
FROM msgsList
JOIN (SELECT MIN(msg_from, msg_to) AS x,
             MAX(msg_from, msg_to) AS y,
             MAX(msg_time) AS msg_time
     FROM msgsList
     GROUP BY x, y) AS m
ON m.x        = MIN(msgsList.msg_from, msgsList.msg_to) AND
   m.y        = MAX(msgsList.msg_from, msgsList.msg_to) AND
   m.msg_time = msgsList.msg_time;

如果你有SQLite 3.7.11或更高版本（not available in all Android versions），你只需使用聚合MAX（）来选择要返回的行：

SELECT *,
       MAX(msg_time)
FROM msgsList
GROUP BY MIN(msg_from, msg_to),
         MAX(msg_from, msg_to);

Answer 2

您可以使用SQLiteDatabse类的rawQuery(String query)按原样运行。

将MySQL查询转换为SQLite

2 个答案: