MYSQL - 加入多个日期 - 只得到第一次从加入

Question

，所以我有3代表在MySQL

事件

| ID | event_name | 
------------------- 
| 1 | test  | 
| 2 | test2 | 
| 3 | test3 | 

sp_events

| ID | event_ID | show_in_grid | 
-------------------------------- 
| 5 | 1  |  1  | 
| 6 | 2  |  1  | 

sp_event_dates

| ID | sp_event_ID |  start_date  | 
------------------------------------------ 
| 1 |  5  | 2016-10-31 14:00:00 | 
| 2 |  5  | 2016-11-01 14:00:00 | 
| 3 |  5  | 2016-11-02 14:00:00 | 
| 4 |  6  | 2016-12-01 14:00:00 | 
| 5 |  6  | 2016-12-02 14:00:00 | 

所以我试图加入sp_event_dates表，但我只想要第一个结果，并不想每个结果重复。

的SQL我用尽是

SELECT events.*, sp_event_dates.start_date FROM events 
JOIN sp_events 
ON sp_events.event_ID=events.ID 
JOIN sp_event_dates ON sp_event_dates.sp_event_ID = 
    (SELECT dd.ID FROM sp_event_dates dd WHERE sp_events.ID = 
    dd.sp_event_ID ORDER BY dd.start_date ASC LIMIT 1) 
WHERE sp_events.show_in_grid=1; 

按预期这不起作用。我希望的结果，下面是：

| ID | event_name |  start_date  | 
----------------------------------------- 
| 1 | test  | 2016-10-31 14:00:00 | 
| 2 | test2 | 2016-12-01 14:00:00 | 

我做的最终计划增加在起始日期where子句，但只是试图让这第一次合作。任何人都可以看到我做错了什么？

我的查询返回任何结果目前

Answer 1

只需使用一个GROUP BY + MIN：

SELECT events.id 
    ,events.event_name 
    ,min(sp_event_dates.start_date) As start_date 
FROM events 
JOIN sp_events 
ON sp_events.event_ID=events.ID 
JOIN sp_event_dates ON sp_event_dates.sp_event_ID = sp_events.ID 
WHERE sp_events.show_in_grid=1 
GROUP BY events.id 
    ,events.event_name 

Answer 2

你需要groupby事件ID

SQL：

SELECT 
    events.ID, 
    events.event_name, 
    sp_event_dates.start_date 
FROM 
    `events` 
    INNER JOIN sp_events 
    ON sp_events.event_ID = events.ID 
    INNER JOIN sp_event_dates 
    ON sp_event_dates.`sp_event_ID` = sp_events.`ID` 
WHERE sp_events.show_in_grid = 1 
GROUP BY events.ID 

输出：

ID event_name start_date   

---

1 test  2016-10-31 14:00:00 
2 test2  2016-12-01 14:00:00