Mysql去重的几种方式分步讲解

create table t_score(
ts datetime,
id varchar(10),
name varchar(255),
score int(3)
)

insert into t_score value(now(), '101','zhangsan', 90);
insert into t_score value(now(), '101','zhangsan', 92);
insert into t_score value(now(), '101','zhangsan', 96);
insert into t_score value(now(), '102','lisi', 90);
insert into t_score value(now(), '102','lisi', 92);
insert into t_score value(now(), '103','wangwu', 96);

SELECT DISTINCT
	( id ),
	NAME,
	score 
FROM
	t_score

SELECT
	id,
	name,
	score 
FROM
	t_score 
GROUP BY
	id,
	name,
	score

SELECT
  a0.*
FROM
  t_score a0
  RIGHT JOIN (
    SELECT
      max(ts) tsMax,
      id
    FROM
      t_score
    GROUP BY
      id
  ) b0 ON a0.ts = b0.tsMax
  AND a0.id = b0.id

SELECT
  a0.*
FROM
  t_score a0
WHERE
  EXISTS (
    SELECT
      *
    FROM
      (
        SELECT
          max(ts) tsMax,
          id
        FROM
          t_score
        GROUP BY
          id
      ) b0
    WHERE
      b0.tsMax = a0.ts
      AND b0.id = a0.id
  )

SELECT
	* 
FROM
	( SELECT *, row_number() over ( PARTITION BY id ORDER BY ts DESC ) num FROM t_score ) a0 
WHERE
	a0.num = 1