Mysql，如何按列分組和 select 最新日期？

Question

從圖中的結果可以看出，BASIC_ADJUSTM 是重復的，我想把它分組，select 只是最新的一個，它的字段值為 2500

Answer 1

您可以按如下方式使用NOT EXISTS ：

SELECT *
  FROM employment_informations t1
 WHERE NOT EXISTS
       (SELECT 1 FROM employment_informations  t2
         WHERE t1.employee_id = t2.employee_id 
           AND t1.field_name = t2.field_name
           AND t2.created_at > t1.created_at)

Answer 2

對於那些想要 select 列的人，這些列不屬於 group by 或不是聚合 function 我是這樣做的：

SELECT *
FROM employment_informations t1
WHERE (t1.employee_id, t1.field_name, t1.created_at) = ANY(
    SELECT 
        t2.employee_id,
        t2.field_name,
        MAX(t2.created_at)
    FROM employment_informations t2
    WHERE t2.effectivity_date = '2021-01-20'
    GROUP BY t2.employee_id, t2.field_name
)
ORDER BY t1.employee_id, t1.field_name