一句SQL, 该怎么优化

Question

SELECT 
  (SELECT 
    MAX(`word_id`) 
  FROM
    `tbl_user_words` 
  WHERE `member_id` = 1) AS max_id,
  (SELECT 
    COUNT(`word_id`) 
  FROM
    `tbl_user_words` 
  WHERE `right_count` < 5 
    AND `member_id` = 1) AS num ;

看起来怪怪的 ～

Answer 1

试试这条语句, 帅气不?

SELECT MAX(`word_id`) AS max_id, SUM(`right_count` < 5) as num
FROM `tbl_user_words` 
WHERE `member_id` = 1;

Answer 2

请将所有语句分开到代码中操作。。。。你看着不头痛么

Answer 3

select max(t1.word_id) as max_id, count(t2.word_id) as num from tbl_user_words as t1, tbl_user_words as t2 where t1.member_id = 1 and t2.member_id = 1 and t2.right_count < 5

这样写可能清晰点。

Answer 4

这样的sql语句效率不高，建议拆分成多条，查询缓存的命中率会高一些。