SQL查询加速

Question

我正在尝试从表中选择N个最后的唯一关键字，该表的结构如下：

id | keyword  | digit
1  | TEXT1    | 123
2  | TEXT2    | 125
...
3  | TEXT3    | 123

with查询：

SELECT id, keyword FROM table 
WHERE digit = 123 
AND id IN 
(SELECT MAX(id) FROM table GROUP by keyword)
ORDER BY id DESC LIMIT 10

当limit为10 - 20时，所需时间不到一秒，但如果limit从50开始，则查询时间从3秒或更长开始。

分选是邪恶的。我是否可以加速这样的查询？

Answer 1

尝尝这个

    SELECT MAX(id) max, keyword FROM table 
    WHERE digit = 123 
    GROUP BY keyword
    ORDER BY max DESC LIMIT 10

Answer 2

尝尝这个

SELECT MAX(id) as id, keyword FROM table
    WHERE digit = 123
    GROUP BY keyword 
    ORDER BY id DESC LIMIT 10

欢迎光临。