mysql分组排序去数据的方式

-- 第一种方式 耗时0.074s
SELECT SQL_NO_CACHE t.* FROM (

SELECT * FROM rocky_b_repaymentrecord ORDER BY ID desc

) t GROUP BY t.user_id;

-- 第二种方式 耗时0.022s

SELECT SQL_NO_CACHE r.* FROM (

SELECT MAX(id) as id FROM rocky_b_repaymentrecord GROUP BY USER_ID

) s LEFT JOIN rocky_b_repaymentrecord r on(s.id = r.ID);

-- 第三种方式 耗时0.154s

SELECT SQL_NO_CACHE r.* FROM rocky_b_repaymentrecord r WHERE EXISTS (

SELECT id FROM (

SELECT MAX(id) as id FROM rocky_b_repaymentrecord GROUP BY USER_ID

) t where t.id = r.id

);