如何优化这个MySQL查询 - 在视图中？性能调整

Question

我有一个带有一些n：m关系表的数据库，我正在使用一个非常大的查询来组合所有这些表。我们先来看看我的数据库：

我创建了两个视图来比较性能。

第一视图：

CREATE VIEW `band_page1` AS (
SELECT maid, band_name, band_logo, band_img, 
    (SELECT countries.country_name from countries WHERE band_info.id_country = countries.id) as country,
    (SELECT locations.location_name from locations WHERE band_info.id_location = locations.id) as location,
    (SELECT status.status_name from status WHERE band_info.id_status = status.id) as status,
    (SELECT founding.fyear from founding WHERE band_info.id_founding = founding.id) as founding,
    (SELECT active.ayear from active WHERE band_info.id_active = active.id) as active,

    (SELECT GROUP_CONCAT(DISTINCT genres.genre_name ORDER BY genres.genre_name) 
     FROM genres LEFT JOIN band_genres ON band_genres.id_genre = genres.id
     WHERE band_genres.id_band = band_info.maid) AS genre,

    (SELECT GROUP_CONCAT(DISTINCT themes.theme_name ORDER BY themes.theme_name) 
     FROM themes LEFT JOIN band_themes ON band_themes.id_theme = themes.id
     WHERE band_themes.id_band = band_info.maid) AS themes,

    (SELECT GROUP_CONCAT(DISTINCT labels.label_name ORDER BY labels.label_name) 
     FROM labels LEFT JOIN band_labels ON band_labels.id_label = labels.id
     WHERE band_labels.id_band = band_info.maid) AS label

FROM band_info
GROUP BY band_info.maid);

第二视图：

CREATE VIEW `band_page2` AS ( 
         SELECT band_info.maid, band_info.band_name, band_info.band_logo, band_info.band_img, 
        (SELECT countries.country_name from countries WHERE band_info.id_country = countries.id) as country, 
        (SELECT locations.location_name from locations WHERE band_info.id_location = locations.id) as location, 
        (SELECT status.status_name from status WHERE band_info.id_status = status.id) as status, 
        (SELECT founding.fyear from founding WHERE band_info.id_founding = founding.id) as founding, 
        (SELECT active.ayear from active WHERE band_info.id_active = active.id) as active, 
        GROUP_CONCAT(DISTINCT genres.genre_name ORDER BY genres.genre_name) AS genre, 
        GROUP_CONCAT(DISTINCT themes.theme_name ORDER BY themes.theme_name) AS themes, 
        GROUP_CONCAT(DISTINCT labels.label_name ORDER BY labels.label_name) AS label 
        FROM band_info 
    LEFT JOIN band_genres ON band_genres.id_band = band_info.maid
    LEFT JOIN band_themes ON band_themes.id_band = band_info.maid
    LEFT JOIN band_labels ON band_labels.id_band = band_info.maid
    LEFT JOIN genres ON genres.id = band_genres.id_genre 
    LEFT JOIN themes ON themes.id = band_themes.id_theme 
    LEFT JOIN labels ON labels.id = band_labels.id_label
    GROUP BY band_info.maid);

当我转到phpmyadmin并打开一个视图时，两个视图都需要3秒才能显示查询结果。我正在使用此视图进行如下查询：

SELECT * FROM band_page1 where maid = '$id';

使用php感觉好像花了很长时间才能得到结果。 它不仅耗时3秒，还需要更长的时间。 我的问题是，我如何优化我的查询？

Answer 1

有过这样的事情：＆＃34;过度规范化＆＃34;。

有标准的＆＃34;国家/地区代码＆＃34;这是2个字母。将它们INT而不是YEAR设置为另一个表格。这将该列从4个字节减少到2个。并且删除了查找。

status是一个2字节的数据类型;不要把这种情况正常化。

考虑将ENUM转换为1字节VIEWs而不是查找。

可能还有其他人。

GROUP BY是语法糖，从不提高性能。有时表现会更差。

我认为首先 VIEW中的band_*没有任何用处。

{{1}}表似乎是多对多映射表。遵循these tips可以提高他们的表现。