为不同的列选择最近的结果-SQL [英] select recent results for distinct columns- SQL

问题描述

大家好，请帮忙

我试图在最新日期获得每辆车的等级.

样本表:

Hi guys, please help

Im trying to get the grade for each car at the latest date.

Sample table:

car-index	installed_date	firebar-grade	frame-grade
CAR5	           05-Jul-12	          B	A
CAR3	           31-Jan-12	          A	A
CAR1	           05-Apr-12	          C	C
CAR1	           24-May-12	          D	D
CAR3	           18-May-12	          C	C
CAR1	           08-Feb-12	          C	A
CAR1	           18-May-12	          C	B
CAR5	           24-May-12	          D	C
CAR3	           11-May-12	          C	B
CAR5	           22-Aug-12	          B	B
CAR5	           17-Sep-12	          A	B

预期结果:

desired results:

car-index	installed_date	firebar-grade	frame-grade
CAR1	            24-May-12	       D	D
CAR3	            18-May-12	       C	C
CAR5	            17-Sep-12	       A	B

我已经尝试过了，但是结果不正确.

I''ve tried this, but the results are incorrect.

select car_index, frame_grade, firebar_grade, max(installed_date) as recentdate from car 
group by car_index, frame_grade, firebar_grade;

推荐答案

select * from car c where c.installed_date = (select MAX(installed_date) from car cr where cr.[car-index] = c.[car-index])

试试这个

Try this

SELECT C.car_index,MAX(C.firebar_grade),MAX(C.frame_grade) FROM Car C 
Group by C.car_index 

希望这会有所帮助，如果是，则接受并投票回答，否则返回您的查询
--Rahul D.

Hope this helps if yes then accept and vote the answer otherwise revert back with your queries
--Rahul D.

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