未找到子句字段上的 MySQL 内部联接答案

【问题标题】：MySQL Inner Join On Clause Field Not Found未找到子句字段上的 MySQL 内部联接
【发布时间】：2014-05-06 12:32:37
【问题描述】：

我当前的表格如下所示：

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  |
| .  |
| .  |
+----+

我有在特定开始日期的特定天数内重复的事件。我目前的查询是：

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

【问题讨论】：

我认为你离开了 A 表，所以你不能设置条件 T.LessonID=E.ID
Planner_lessons 和 A 没有 on 子句或内/外连接语法
不要混合隐式（逗号）和显式连接语法。事实上，根本不要使用隐式连接语法。另外，我怀疑将 'id' 与 DATEDIFF('2014-05-30 00:00:00','2014-05-05 00:00:00') 的结果进行比较会更有效

标签： mysql sql datetime inner-join repeat

【解决方案1】：

这是您的查询，格式化以便人们可以阅读：

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 范围规则，E 中的列在逗号后无法识别。

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 切换为内部联接，因为where 子句撤消了外部联接。

【讨论】：

【解决方案2】：

您错过了别名为 A 的子查询的 JOIN 条件。假设 Planner_Tally 表包含列 ID ，您可以添加连接条件 ON A.ID=E.ID 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

【讨论】：

【解决方案3】：

顺便说一句，考虑以下...（ints 是一个从 0 到 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)

如您所见，尽管两个查询在逻辑上相同，但第一个为possible_keys 注册了NULL。

我们现在已经达到了我对索引的全部了解。

【讨论】：