查询 - 从其他表的最新日期和链接数据

Question

n_station

code_stas nom_station 
1   StationA 
2   StationB 
3   StationC 

val_horaire

code_mesure date_val_hor h_01 h_02 h_03 
1   14/11/2016  23  29  32 
1   15/11/2016  45  47  35 
2   14/11/2016  12  15  13 
2   15/11/2016  21  23  19 
3   14/11/2016  74  75  79 

我想获得表的最新（日期）行val_horaire和加入收藏夹n_station

结果

cod_stas nom_station date_val_hor h_01 h_02 h_03 
1   StationA 15/11/2016  45  47  35 
2   StationB 15/11/2016  21  23  19 
3   StationC 14/11/2016  74  75  79 

我该如何做到这一点？下面的查询不起作用

SELECT st.code_stas, st.nom_station, max(vh.date_val_hor), vh.h_01, vh.h_02, vh.h_03 
FROM n_station st 
INNER JOIN val_horaire vh 
ON st.code_stas = vh.code_mesure 
GROUP BY st.code_stas, st.nom_station, vh.h_01, vh.h_02, vh.h_03 

这将多次告诉我一个站

Answer 1

解决方案一：

SELECT 
    st.code_stas, 
    st.nom_station, 
    MAX(vh.date_val_hor) KEEP(DENSE_RANK FIRST ORDER BY st.nom_station DESC) AS date_val_hor, 
    MAX(vh.h_01) KEEP(DENSE_RANK FIRST ORDER BY st.nom_station DESC) AS h_01, 
    MAX(vh.h_02) KEEP(DENSE_RANK FIRST ORDER BY st.nom_station DESC) AS h_02, 
    MAX(vh.h_03) KEEP(DENSE_RANK FIRST ORDER BY st.nom_station DESC) AS h_03 
FROM 
    n_station st, 
    val_horaire vh 
WHERE 
    st.code_stas = vh.code_mesure 
GROUP BY st.code_stas, st.nom_station 

解决方案2号：

SELECT code_stas, nom_station, h_01, h_02, h_03 FROM (
    SELECT 
     st.code_stas, 
     st.nom_station, 
     vh.date_val_hor, 
     vh.h_01, 
     vh.h_02, 
     vh.h_03, 
     ROW_NUMBER() OVER(PARTITION BY st.code_stas, st.nom_station ORDER BY vh.date_val_hor DESC) AS DISTINCT_FLG 
    FROM 
     n_station st, 
     val_horaire vh 
    WHERE 
     st.code_stas = vh.code_mesure 
) 
WHERE DISTINCT_FLG = 1 

Answer 2

是这样的（？）：

SELECT st.code_stas, st.nom_station, zzz.MAX_date_val_hor, vh.h_01, vh.h_02, vh.h_03 
FROM (SELECT code_mesure, MAX(date_val_hor) AS MAX_date_val_hor FROM val_horaire GROUP BY code_mesure) ZZZ 
INNER JOIN 
n_station st ON st.code_stas=zzz.code_mesure 
INNER JOIN val_horaire vh 
ON st.code_stas = vh.code_mesure 
GROUP BY st.code_stas, st.nom_station, zzz.MAX_date_val_hor, vh.h_01, vh.h_02, vh.h_03;