Question

所以，我的初始查询就像这样：

SELECT 
    `surveyEntries`.`ID` AS EntryID,
    `surveyEntries`.`created` AS EntryDate,
    `hw_services`.`name` AS Provider, 
    `surveyQuestions`.`ID` AS QuestionID,
    `surveyQuestions`.`label` AS Question, 
    `survey_meta`.`answer` AS Answer,
    `surveyQuestions`.`parentID` AS ParentQuestion
FROM `survey` , `surveyQuestions` , `surveyEntries` , `survey_meta` , `hw_services`
WHERE `survey`.`ID` =2
    AND `survey`.`ID` = `surveyQuestions`.`surveyID`
    AND `survey`.`ID` = `surveyEntries`.`surveyID`
    AND `surveyEntries`.`ID` = `survey_meta`.`entryID`
    AND `hw_services`.`ID` = `surveyEntries`.`hw_serviceID`
    AND `surveyQuestions`.`ID` = `survey_meta`.`questionID`

现在我已经阅读过，这是一个非常弱的冗长查询，可以进行优化。

有谁知道我怎么做到这一点？我的尝试未能提供下面相同的结果：

SELECT 
    `surveyEntries`.`ID` AS EntryID,
    `surveyEntries`.`created` AS EntryDate,
    `hw_services`.`name` AS Provider,
    `surveyQuestions`.`ID` AS QuestionID,
    `surveyQuestions`.`label` AS Question,
    `survey_meta`.`answer` AS Answer,
    `surveyQuestions`.`parentID` AS ParentQuestion
FROM `survey`
    JOIN `surveyQuestions` 
        ON `survey`.`ID` = `surveyQuestions`.`surveyID`
    JOIN `surveyEntries`
        ON `survey`.`ID` = `surveyEntries`.`surveyID`
    JOIN `survey_meta`
        ON `survey`.`ID` = `survey_meta`.`entryID`
    JOIN `hw_services` 
        ON `survey`.`ID` = `hw_services`.`ID`
WHERE `survey`.`ID` =2

修改::

好的，所以看了你的评论之后我就能明白为什么，愚蠢的错误。

一些连接实际上是将两个表连接在一起，而不是将它们连接到FROM表（调查）。

这是我失败的新尝试。

SELECT 
`surveyEntries`.`ID` AS EntryID,
`surveyEntries`.`created` AS EntryDate,
`hw_services`.`name` AS Provider,
`surveyQuestions`.`ID` AS QuestionID,
`surveyQuestions`.`label` AS Question,
`survey_meta`.`answer` AS Answer,
`surveyQuestions`.`parentID` AS ParentQuestion
FROM `survey`
JOIN `surveyQuestions` 
    ON `survey`.`ID` = `surveyQuestions`.`surveyID`

JOIN `surveyEntries`
    ON `survey`.`ID` = `surveyEntries`.`surveyID`

JOIN `survey_meta`
    ON `surveyEntries`.`surveyID` = `survey_meta`.`entryID`

JOIN `hw_services` 
    ON `hw_services`.`ID` = `surveyEntries `.`hw_serviceID`

JOIN `surveyQuestions` 
    ON `surveyQuestions`.`ID` = `survey_meta`.`questionID`

WHERE `survey`.`ID` =2

我得到的错误是：不唯一的表/别名：'surveyQuestions'

Answer 1

试试这个：

SELECT 
`surveyEntries`.`ID` AS EntryID,
`surveyEntries`.`created` AS EntryDate,
`hw_services`.`name` AS Provider,
`surveyQuestions`.`ID` AS QuestionID,
`surveyQuestions`.`label` AS Question,
`survey_meta`.`answer` AS Answer,
`surveyQuestions`.`parentID` AS ParentQuestion
FROM `survey`
JOIN `surveyQuestions` 
    ON `survey`.`ID` = `surveyQuestions`.`surveyID`
JOIN `surveyEntries`
    ON `survey`.`ID` = `surveyEntries`.`surveyID`
JOIN `survey_meta`
     ON (`surveyEntries`.`ID` = `survey_meta`.`entryID` AND `surveyQuestions`.`ID` = `survey_meta`.`questionID`)
JOIN `hw_services` 
    ON `surveyEntries`.`hw_serviceID` = `hw_services`.`ID`
WHERE `survey`.`ID` =2

使mysql查询更有效率

1 个答案: