Question

要求是按日期获取不同且最新的记录。有些记录具有相同的Basket id，但其他信息是唯一的。根据我的方法，我可以获得按照篮子ID分组的desc日期排序的记录，但我不知道如何获得满足我要求的那些排序记录的TOP 1。请建议如何实现这一目标。

ID  Flower        Country           Date
==================================================

A12   Rose            China          2016:08:18 16:02:19
A65   Turnip          China          2016:08:25 18:25:54
A11   unknown         China          2016:08:18 16:45:27
A43   angelica        Mexico         2016:08:25 18:25:54
A43   Rose            Mexico         2016:08:25 15:46:35
A43   angelica         Mexico        2016:08:19 12:33:43
A43   Rose            Mexico         2016:08:18 16:23:01
A44   solomon         Denmark        2016:08:22 18:49:10
A44   Turnip          Denmark        2016:08:18 09:44:06
A49   duetzia         Mexico         2016:08:23 21:25:38
A49   Rose            Mexico         2016:08:23 18:54:55
A49   angelica        Mexico         2016:08:19 12:23:58
A49   Rose            Mexico         2016:08:18 16:23:01
B15   solomon         Denmark        2016:08:22 18:58:35
B43   solomon         Denmark        2016:08:24 20:00:14
B43   Turnip          Denmark        2016:08:22 13:57:08
B43   impCalamus      Denmark        2016:08:18 17:28:53
B43   impCalamus      Denmark        2016:08:18 15:40:45
B45   solomon         Denmark        2016:08:24 20:00:14


Expected output
===============
ID  Flower        Country           Date
=============================================                      
A11   unknown         China          2016:08:18 16:45:27
A12   Rose            China          2016:08:18 16:02:19
A43   angelica        Mexico         2016:08:25 18:25:54
A44   solomon         Denmark        2016:08:22 18:49:10
A49   duetzia         Mexico         2016:08:23 21:25:38
A65   Turnip          China          2016:08:25 18:25:54
B15   solomon         Denmark        2016:08:22 18:58:35
B43   solomon         Denmark        2016:08:24 20:00:14
B45   solomon         Denmark        2016:08:24 20:00:14


Steps to create the Table.
---------------------------
CREATE TABLE FLOWER( ID varchar(12) , FLOWER varchar(12), COUNTRY varchar(12), DATE TIME);

INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A12', 'Rose', 'China', '2016:08:18 16:02:19' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A65', 'Turnip'       , 'China'         , '2016:08:25 18:25:54' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A11', 'unknown'      , 'China'         , '2016:08:18 16:45:27' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A43', 'angelica'     , 'Mexico'        , '2016:08:25 18:25:54' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A43', 'Rose'         , 'Mexico'        , '2016:08:25 15:46:35' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A43', 'angelica'     , 'Mexico'        , '2016:08:19 12:33:43' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A43', 'Rose'         , 'Mexico'        , '2016:08:18 16:23:01' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A44', 'solomon'      , 'Denmark'       , '2016:08:22 18:49:10' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A44', 'Turnip'       , 'Denmark'       , '2016:08:18 09:44:06' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A49', 'duetzia'      , 'Mexico'        , '2016:08:23 21:25:38' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A49', 'Rose'         , 'Mexico'        , '2016:08:23 18:54:55' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A49', 'angelica'     , 'Mexico'        , '2016:08:19 12:23:58' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('A49', 'Rose'         , 'Mexico'        , '2016:08:18 16:23:01' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('B15', 'solomon'      , 'Denmark'       , '2016:08:22 18:58:35' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('B43', 'solomon'      , 'Denmark'       , '2016:08:24 20:00:14' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('B43', 'Turnip'       , 'Denmark'       , '2016:08:22 13:57:08' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('B43', 'impCalamus'   , 'Denmark'       , '2016:08:18 17:28:53' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('B43', 'impCalamus'   , 'Denmark'       , '2016:08:18 15:40:45' );
INSERT INTO FLOWER (ID,FLOWER,COUNTRY,DATE) VALUES ('B45', 'solomon'      , 'Denmark'       , '2016:08:24 20:00:14' );


My Approach
===========

select * from flower group by id, date order by id ,date desc;

 ID          FLOWER      COUNTRY     DATE
----------  ----------  ----------  -------------------
A11         unknown     China       2016:08:18 16:45:27 <---
A12         Rose        China       2016:08:18 16:02:19 <---
A43         angelica    Mexico      2016:08:25 18:25:54 <---
A43         Rose        Mexico      2016:08:25 15:46:35
A43         angelica    Mexico      2016:08:19 12:33:43
A43         Rose        Mexico      2016:08:18 16:23:01
A44         solomon     Denmark     2016:08:22 18:49:10 <---
A44         Turnip      Denmark     2016:08:18 09:44:06
A49         duetzia     Mexico      2016:08:23 21:25:38 <---
A49         Rose        Mexico      2016:08:23 18:54:55
A49         angelica    Mexico      2016:08:19 12:23:58
A49         Rose        Mexico      2016:08:18 16:23:01
A65         Turnip      China       2016:08:25 18:25:54 <---
B15         solomon     Denmark     2016:08:22 18:58:35 <---
B43         solomon     Denmark     2016:08:24 20:00:14 <---
B43         Turnip      Denmark     2016:08:22 13:57:08
B43         impCalamus  Denmark     2016:08:18 17:28:53
B43         impCalamus  Denmark     2016:08:18 15:40:45
B45         solomon     Denmark     2016:08:24 20:00:14 <---

标有箭头＆lt; ----的那些是我感兴趣的人。

Answer 1

您可以使用where子句和相关子查询来执行此操作：

select t.*
from t
where t.time = (select max(t2.time)
                from t t2
                where t2.id = t.id
               );

sqlite3查询在排序记录中查找不同的前1位

1 个答案: