Question

我目前的表格如下：

Lessons:
+-----------------------------------+
| ID | Name  | StartDate  | Repeats |
|----|-------|------------|---------|
| 1  | Maths | 2014-05-05 |    5    |
| 2  | Lunch | 2014-05-05 |    1    |
| 3  | Comp  | 2014-05-05 |    7    |
+-----------------------------------+

LessonTimes:
+-------------------------------------+
| ID | LessonID | StartTime | EndTime |
|----|----------|-----------|---------|
| 1  |    1     | 10:00:00  |    5    |
| 2  |    2     | 12:25:00  |    1    |
| 3  |    3     | 14:00:00  |    7    |
+-------------------------------------+

Tally:
+----+
| ID |
|----|
| 1  |
| 2  |
| .  |
| .  |
+----+

我的活动会在特定天数内以特定的开始日期重复。我当前的查询是：

SELECT E.ID
     , E.Name
     , E.StartDate
     , E.Repeats
     , A.ShowDate
     , DATEDIFF(E.StartDate, A.ShowDate) diff
     , T.StartTime
     , DATE_ADD(A.ShowDate, INTERVAL T.StartTime HOUR_SECOND) ShowTime 
  FROM Planner_Lessons E
     , ( SELECT DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY ) ShowDate
           FROM `Planner_Tally`
          WHERE (DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY )<= '2014-05-30 00:00:00')
          ORDER 
             BY Id ASC 
       ) A 
    LEFT 
    JOIN Planner_LessonTimes T 
      ON T.LessonID = E.ID 
   WHERE MOD(DATEDIFF(E.StartDate, A.ShowDate), E.Repeats) = 0 
     AND A.ShowDate >= E.StartDate

但我得到的错误是在“ON”子句中找不到字段E.ID。

我发现查询的原始问题在这里 - PHP/MySQL: Model repeating events in a database but query for date ranges

Answer 1

这是您的查询格式，以便人们可以阅读：

SELECT E.ID, E.Name, E.StartDate, E.Repeats, A.ShowDate, DATEDIFF(E.StartDate, A.ShowDate) AS diff,
       T.StartTime, DATE_ADD(A.ShowDate, INTERVAL T.StartTime HOUR_SECOND) AS ShowTime
FROM Planner_Lessons AS E,
     (SELECT DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY) as ShowDate
      FROM `Planner_Tally`
      WHERE (DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY)<='2014-05-30 00:00:00')
      ORDER BY Id ASC
     ) A LEFT JOIN
     Planner_LessonTimes AS T
     ON T.LessonID=E.ID
WHERE MOD(DATEDIFF(E.StartDate, A.ShowDate), E.Repeats)=0 AND A.ShowDate>=E.StartDate;

您缺少隐式和显式join语法。由于MySQL的作用域规则，逗号后无法识别E中的列。

SELECT E.ID, E.Name, E.StartDate, E.Repeats, A.ShowDate, DATEDIFF(E.StartDate, A.ShowDate) AS diff,
       T.StartTime, DATE_ADD(A.ShowDate, INTERVAL T.StartTime HOUR_SECOND) AS ShowTime
FROM Planner_Lessons E JOIN
     Planner_LessonTimes T
     ON T.LessonID = E.ID JOIN
     (SELECT DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY) as ShowDate
      FROM `Planner_Tally`
      WHERE (DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY)<='2014-05-30 00:00:00')
      ORDER BY Id ASC
     ) A 
     ON MOD(DATEDIFF(E.StartDate, A.ShowDate), E.Repeats)=0 AND A.ShowDate>=E.StartDate;

我将left join切换为内连接，因为where子句撤消了外连接。

Answer 2

您错过了子查询别名为 A 的JOIN条件。假设Planner_Tally表包含列ID，您可以在A.ID=E.ID添加加入条件，如下所示

SELECT E.ID, E.Name, E.StartDate, E.Repeats, A.ShowDate, 
       DATEDIFF(E.StartDate, A.ShowDate) AS diff, T.StartTime,
       DATE_ADD(A.ShowDate, INTERVAL T.StartTime HOUR_SECOND) AS ShowTime 
FROM Planner_Lessons AS E
LEFT JOIN Planner_LessonTimes AS T ON T.LessonID=E.ID 
LEFT JOIN (
           SELECT DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY) as ShowDate,ID
           FROM `Planner_Tally`
           WHERE (DATE_ADD('2014-05-05 00:00:00',INTERVAL ID DAY)<='2014-05-30 00:00:00')
 ) A  ON A.ID=E.ID 
WHERE MOD(DATEDIFF(E.StartDate, A.ShowDate), E.Repeats)=0 
      AND A.ShowDate>=E.StartDate
ORDER BY E.Id ASC

Answer 3

顺便说一句，请考虑以下内容......（ints是0-9的整数表）

EXPLAIN
SELECT * FROM ints WHERE '2014-05-05 00:00:00' + INTERVAL i DAY < '2014-30-30 00:00:00'\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: ints
         type: index
possible_keys: NULL
          key: PRIMARY
      key_len: 4
          ref: NULL
         rows: 10
        Extra: Using where; Using index
1 row in set (0.00 sec)

EXPLAIN
SELECT * FROM ints WHERE i < DATEDIFF('2014-05-30 00:00:00','2014-05-05 00:00:00')\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: ints
         type: index
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 4
          ref: NULL
         rows: 10
        Extra: Using where; Using index
1 row in set (0.00 sec)

正如您所看到的，虽然两个查询在逻辑上是相同的，但第一个查询为possible_keys注册NULL。

我们现在已经达到了我对指数的全面了解。

MySQL内部联接未找到子句字段

3 个答案: