在 PostgreSQL 中计算以前的结果答案

【问题标题】：Calculate previous results in PostgreSQL在 PostgreSQL 中计算以前的结果
【发布时间】：2016-05-01 01:30:02
【问题描述】：

我正在尝试完成一项有趣的研究，并向现有数据集添加新功能

ID      DATE           LEAGUE         HOME        AWAY    H_GOALS A_GOALS PREV_H_GOALS PREV_A_GOALS
9911 "2005-01-01" "Bundesliga 1" "Wolfsburg"  "Schalke 04"    2      1          NULL      NULL
9822 "2005-01-01" "Jupiler League" "Beveren" "Lokeren"        2      1          NULL      NULL
9823 "2005-01-01" "Jupiler League" "Waregem" "Westerlo"       2      3          NULL      NULL
9824 "2005-01-10" "Jupiler League" "Westerlo" "Beveren"       4      1           3         2
9932 "2005-01-10" "Bundesliga 1" "Bayern Munich" "Wolfsburg"  2      0          NULL       2
9933 "2005-01-10" "Bundesliga 1" "Ein Frankfurt" "Schalke 04" 0      1          NULL       1

现在，我想添加额外的列，例如

MATCH_GOALS - 该队在上一场比赛中的进球
PREV_RESULT - 上一场比赛的结果[1-赢，2-平，3-输]
ALL_GOALS_IN_SEASON - 本赛季球队总进球数

我对案例 #1 的尝试不正确：

SELECT ROW_NUMBER() OVER (ORDER BY start_time DESC) AS rowno,
       LEAD(m.match_score) OVER (ORDER BY start_time DESC) as MATCH_GOALS, -- #1

FROM match as m
WHERE (m.home = m.home OR m.away = m.away) #fail
ORDER BY start_time DESC

您能否建议适当的窗口函数（PostgreSQL）或固定示例？

【问题讨论】：

您的问题不清楚。每行对应两个团队。您要考虑哪个团队？
我正在寻找两个团队的先前信息

标签： python sql postgresql python-2.7 pandas

【解决方案1】：

我在SQL Server 中测试了一个解决方案，但我看到PostgreSQL 支持 SQL Server 中的所有好东西（CTE、窗口函数等），所以这应该是一个好的开始。

您的数据结构对于直接窗口函数组件非常不友好，因此CTE 以更容易处理的方式获得它：

ID, Date, League, Team, Goals

这允许获取以前的信息，因为团队存在于单个列中。

此外，首先CTE 计算球队在该特定比赛中的成绩。

第二个CTE 实际上使用LAG 窗口函数获取有关先前匹配的信息。

;with PivCTE AS (
    SELECT ID, Date, League, Home AS Team, HGoals AS Goals, 
        (CASE WHEN HGoals > AGoals THEN 1 WHEN HGoals = AGoals THEN 2 ELSE 3 END) AS Result,
        SUM(HGoals) OVER (PARTITION BY Home ORDER BY (SELECT 1)) AS AllGoals
    FROM Match 
    UNION
    SELECT ID, Date, League, Away AS Team, AGoals AS Goals,
        (CASE WHEN HGoals < AGoals THEN 1 WHEN HGoals = AGoals THEN 2 ELSE 3 END) AS Result,
        SUM(AGoals) OVER (PARTITION BY Away ORDER BY (SELECT 1)) AS AllGoals 
    FROM Match
),
PrevData AS (
    SELECT ID, Date, League, Team, 
        LAG(Goals, 1, NULL) OVER (PARTITION BY Team ORDER BY Date) AS PrevGoals,
        LAG(Result, 1, NULL) OVER (PARTITION BY Team ORDER BY Date) AS PrevResult,
        AllGoals
    FROM PivCTE
)
select M.*, 
    PH.PrevGoals AS HomePrevGoals, PA.PrevGoals AS AwayPrevGoals, 
    PH.PrevResult AS HomePrevWin, PA.PrevResult AS AwayPrevWin,
    PH.AllGoals AS HomeAllGoals, PA.AllGoals AS AwayAllGoals
FROM Match M
    JOIN PrevData PH ON PH.ID = M.ID AND PH.Team = M.Home
    JOIN PrevData PA ON PA.ID = M.ID AND PA.Team = M.Away
ORDER BY M.Date DESC

设置数据：

create table Match (
    ID INT NOT NULL,
    Date DATE NOT NULL,
    League NVARCHAR(100) NOT NULL,
    Home NVARCHAR(100) NOT NULL,
    Away NVARCHAR(100) NOT NULL,
    HGoals INT NOT NULL,
    AGoals INT NOT NULL
)

insert into Match values 

(9911, '2005-01-01', 'Bundesliga 1', 'Wolfsburg',  'Schalke 04',    2,      1),
(9822, '2005-01-01', 'Jupiler League', 'Beveren', 'Lokeren',        2,      1),
(9823, '2005-01-01', 'Jupiler League', 'Waregem', 'Westerlo',       2,      3),
(9824, '2005-01-10', 'Jupiler League', 'Westerlo', 'Beveren',       4,      1),
(9932, '2005-01-10', 'Bundesliga 1', 'Bayern Munich', 'Wolfsburg',  2,      0),
(9933, '2005-01-10', 'Bundesliga 1', 'Ein Frankfurt', 'Schalke 04', 0 ,     1)

【讨论】：