Question

我有一个表，该表的标签引用了多种语言的另一个表。我编写了此查询，该查询可以完成工作，但并不优雅，而且查询时间长：

SELECT DISTINCT
    T1.ID as CountryID,
    T1.Type AS CountryType,
    T2.Text AS CountryText,
    T3.Text AS CountryTitle,
    T4.Text AS Heading1,
    T5.Text AS Heading2,
    T6.Text AS Heading3,
    T7.Text AS Heading4,
    T8.Text AS Heading5,
    T9.Text AS Heading6,
    T10.Text AS Heading7,
    T11.Text AS Heading8,
    T12.Text AS Heading9,
    T13.Text AS Heading10,
    T14.Text AS Heading11,
    T15.Text AS Heading12,
    T16.Text AS Heading13,
    T17.Text AS Heading14,
    T18.Text AS Heading15,
    T19.Text AS Heading16,
    T20.Text AS Heading17,
    T21.Text AS Heading18,
    T22.Text AS Heading19,
    T23.Text AS Heading20
FROM 
    Countrys AS T1
    LEFT JOIN EN_TEXT AS T2 ON T1.DESCRIPTION=T2.TAG
    LEFT JOIN EN_TEXT AS T3 ON CONCAT(T1.COUNTRYTAG,'_TITLE')=T3.TAG
    LEFT JOIN EN_TEXT AS T4 ON CONCAT(T1.COUNTRYTAG,'_HEADING_1')=T4.TAG
    LEFT JOIN EN_TEXT AS T5 ON CONCAT(T1.COUNTRYTAG,'_HEADING_2')=T5.TAG
    LEFT JOIN EN_TEXT AS T6 ON CONCAT(T1.COUNTRYTAG,'_HEADING_3')=T6.TAG
    LEFT JOIN EN_TEXT AS T7 ON CONCAT(T1.COUNTRYTAG,'_HEADING_4')=T7.TAG
    LEFT JOIN EN_TEXT AS T8 ON CONCAT(T1.COUNTRYTAG,'_HEADING_5')=T8.TAG
    LEFT JOIN EN_TEXT AS T9 ON CONCAT(T1.COUNTRYTAG,'_HEADING_6')=T9.TAG
    LEFT JOIN EN_TEXT AS T10 ON CONCAT(T1.COUNTRYTAG,'_HEADING_7')=T10.TAG
    LEFT JOIN EN_TEXT AS T11 ON CONCAT(T1.COUNTRYTAG,'_HEADING_8')=T11.TAG
    LEFT JOIN EN_TEXT AS T12 ON CONCAT(T1.COUNTRYTAG,'_HEADING_9')=T12.TAG
    LEFT JOIN EN_TEXT AS T13 ON CONCAT(T1.COUNTRYTAG,'_HEADING_10')=T13.TAG
    LEFT JOIN EN_TEXT AS T14 ON CONCAT(T1.COUNTRYTAG,'_HEADING_11')=T14.TAG
    LEFT JOIN EN_TEXT AS T15 ON CONCAT(T1.COUNTRYTAG,'_HEADING_12')=T15.TAG
    LEFT JOIN EN_TEXT AS T16 ON CONCAT(T1.COUNTRYTAG,'_HEADING_13')=T16.TAG
    LEFT JOIN EN_TEXT AS T17 ON CONCAT(T1.COUNTRYTAG,'_HEADING_14')=T17.TAG
    LEFT JOIN EN_TEXT AS T18 ON CONCAT(T1.COUNTRYTAG,'_HEADING_15')=T18.TAG
    LEFT JOIN EN_TEXT AS T19 ON CONCAT(T1.COUNTRYTAG,'_HEADING_16')=T19.TAG
    LEFT JOIN EN_TEXT AS T20 ON CONCAT(T1.COUNTRYTAG,'_HEADING_17')=T20.TAG
    LEFT JOIN EN_TEXT AS T21 ON CONCAT(T1.COUNTRYTAG,'_HEADING_18')=T21.TAG
    LEFT JOIN EN_TEXT AS T22 ON CONCAT(T1.COUNTRYTAG,'_HEADING_19')=T22.TAG
    LEFT JOIN EN_TEXT AS T23 ON CONCAT(T1.COUNTRYTAG,'_HEADING_20')=T23.TAG
WHERE
    T1.Type='Country_ENGLAND';

有没有一种方法可以简化此查询，使我不必拥有所有这些左联接？不同的国家/地区会有不同的标题，因此我必须获得所有可能的标题，以确保我能全部理解。

类似的事情-我知道这行不通，我只是举一个我想做的事的例子。

SELECT DISTINCT
T1.ID as CountryID,
T1.Type AS CountryType,
T2.Text AS CountryText,
T3.Text AS CountryTitle,
T4.Text AS Headings?,

FROM 
Countrys AS T1
LEFT JOIN EN_TEXT AS T2 ON T1.DESCRIPTION=T2.TAG
LEFT JOIN EN_TEXT AS T3 ON CONCAT(T1.COUNTRYTAG,'_TITLE')=T3.TAG
LEFT JOIN EN_TEXT AS T4 ON CONCAT(T1.COUNTRYTAG,'_HEADING_%')=T4.TAG AND T4.TAG IS NOT NULL,
WHERE
T1.Type='Country_ENGLAND';

Answer 1

您可以使用条件聚合来旋转标签

server.connection-timeout

好吧，它还是有点缠绕。
但是它只需要1个join，因此它应该更快。

在CASE的条件中，您可以改用SELECT DISTINCT C.ID as CountryID, C.Type AS CountryType, MAX(CASE WHEN C.DESCRIPTION = T.TAG THEN T.Text END) AS CountryText, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_TITLE') THEN T.Text END) AS CountryTitle, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_1') THEN T.Text END) AS Heading1, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_2') THEN T.Text END) AS Heading2, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_3') THEN T.Text END) AS Heading3, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_4') THEN T.Text END) AS Heading4, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_5') THEN T.Text END) AS Heading5, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_6') THEN T.Text END) AS Heading6, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_7') THEN T.Text END) AS Heading7, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_8') THEN T.Text END) AS Heading8, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_9') THEN T.Text END) AS Heading9, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_10') THEN T.Text END) AS Heading10, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_11') THEN T.Text END) AS Heading11, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_12') THEN T.Text END) AS Heading12, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_13') THEN T.Text END) AS Heading13, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_14') THEN T.Text END) AS Heading14, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_15') THEN T.Text END) AS Heading15, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_16') THEN T.Text END) AS Heading16, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_17') THEN T.Text END) AS Heading17, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_18') THEN T.Text END) AS Heading18, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_19') THEN T.Text END) AS Heading19, MAX(CASE WHEN T.TAG = CONCAT(C.COUNTRYTAG,'_HEADING_20') THEN T.Text END) AS Heading20 FROM Countrys AS C LEFT JOIN EN_TEXT AS T ON T.TAG LIKE CONCAT(C.COUNTRYTAG,'%') -- AND (T.TAG LIKE '%TITLE' OR T.TAG LIKE '%HEADING%') WHERE C.Type = 'Country_ENGLAND' GROUP BY C.ID, C.Type;。
因为LIKE子句已经确保了COUNTRYTAG。

F.e。

ON

但是接下来，您将不得不冒风险，... MAX(CASE WHEN T.TAG LIKE '%HEADING_1' THEN T.Text END) AS Heading1, ...中的下划线LIKE是任意1个字符的占位符。

简化具有许多左联接的MySQL查询

1 个答案: