【group by 之后去重，某个字段展示最后一次的值】sql怎么写

一、group by语句，巧用Max

实现效果：group by 之后去重，多条条件相同数据变为一条，判断多条数据的某些字段，只要有为1的就为1

SELECT 
  id,
  name, 
  CASE WHEN MAX(status1) = 1 THEN 1 ELSE 0 END AS status1,
  CASE WHEN MAX(status2) = 1 THEN 1 ELSE 0 END AS status2,
  CASE WHEN MAX(status3) = 1 THEN 1 ELSE 0 END AS status3
FROM 
  your_table
GROUP BY
  id, name;

二、巧用SUBSTRING_INDEX+GROUP_CONCAT

实现效果：还有某个字段，为字符串格式，取最近一条的那一条。

SELECT
  id,
  name,
  CASE WHEN MAX(status1) = 1 THEN 1 ELSE 0 END AS status1,
  CASE WHEN MAX(status2) = 1 THEN 1 ELSE 0 END AS status2,
  CASE WHEN MAX(status3) = 1 THEN 1 ELSE 0 END AS status3,
  SUBSTRING_INDEX(GROUP_CONCAT(field_str ORDER BY id DESC), ',', 1) AS field_str
FROM
  your_table
GROUP BY
  id, name;