我正在尝试编写一个查询来获取类(class)信息以及预订和参加者的数量。每个类(class)可以有多个预订,每个预订可以有多个参加者。
我们已经有了一份工作报告,但它使用多个查询来获取所需的信息。一种用于获取类(class),一种用于获取预订,一种用于获取参加人数。由于数据库的大小已经增大,这非常慢。
报告有许多额外条件:
- 预订人数必须超过 5 人 分钟前,或已确认
- 预订不得取消
- 不得将类(class)标记为已删除
- 类(class)地点必须
LIKE
搜索字符串 - 未预订的类(class)必须出现在结果中
这是表结构:(我省略了不需要的信息。所有字段不为空且没有默认值)
mysql> 描述first_aid_courses;
+------------------+--------------+-----+----------------+
| Field | Type | Key | Extra |
+------------------+--------------+-----+----------------+
| id | int(11) | PRI | auto_increment |
| course_date | date | | |
| region_id | int(11) | | |
| location | varchar(255) | | |
| venue | varchar(255) | | |
| number_of_spaces | int(11) | | |
| deleted | tinyint(1) | | |
+------------------+--------------+-----+----------------+
mysql> 描述first_aid_bookings;
+-----------------------+--------------+-----+----------------+
| Field | Type | Key | Extra |
+-----------------------+--------------+-----+----------------+
| id | int(11) | PRI | auto_increment |
| first_aid_course_id | int(11) | | |
| placed | datetime | | |
| confirmed | tinyint(1) | | |
| cancelled | tinyint(1) | | |
+-----------------------+--------------+-----+----------------+
mysql> 描述first_aid_attendees;
+----------------------+--------------+-----+----------------+
| Field | Type | Key | Extra |
+----------------------+--------------+-----+----------------+
| id | int(11) | PRI | auto_increment |
| first_aid_booking_id | int(11) | | |
+----------------------+--------------+-----+----------------+
mysql> 描述区域;
+----------+--------------+-----+----------------+
| Field | Type | Key | Extra |
+----------+--------------+-----+----------------+
| id | int(11) | PRI | auto_increment |
| name | varchar(255) | | |
+----------+--------------+-----+----------------+
我需要选择以下内容:
Course ID: first_aid_courses.id
Date: first_aid_courses.course_date
Region regions.name
Location: first_aid_courses.location
Bookings: COUNT(first_aid_bookings)
Attendees: COUNT(first_aid_attendees)
Spaces Remaining: COUNT(first_aid_bookings) - COUNT(first_aid_attendees)
这是我到目前为止所拥有的:
SELECT `first_aid_courses`.*,
COUNT(`first_aid_bookings`.`id`) AS `bookings`,
COUNT(`first_aid_attendees`.`id`) AS `attendees`
FROM `first_aid_courses`
LEFT JOIN `first_aid_bookings`
ON `first_aid_courses`.`id` =
`first_aid_bookings`.`first_aid_course_id`
LEFT JOIN `first_aid_attendees`
ON `first_aid_bookings`.`id` =
`first_aid_attendees`.`first_aid_booking_id`
WHERE ( `first_aid_courses`.`location` LIKE '%$search_string%'
OR `first_aid_courses`.`venue` LIKE '%$search_string%' )
AND `first_aid_courses`.`deleted` = 0
AND ( `first_aid_bookings`.`placed` > '$five_minutes_ago'
AND `first_aid_bookings`.`cancelled` = 0
OR `first_aid_bookings`.`confirmed` = 1 )
GROUP BY `first_aid_courses`.`id`
ORDER BY `course_date` DESC
它不太有效,任何人都可以帮助我编写正确的查询吗?此外,该数据库中有 1000 行,因此任何有关使其快速运行的帮助都会受到赞赏(例如要索引哪些字段)。
最佳答案
好的,我已经回答了我自己的问题。有时提出问题有助于您找出答案。
SELECT `first_aid_courses`.*,
`regions`.`name` AS `region_name`,
COUNT(DISTINCT `first_aid_bookings`.`id`) AS `bookings`,
COUNT(`first_aid_attendees`.`id`) AS `attendees`
FROM `first_aid_courses`
JOIN `regions`
ON `first_aid_courses`.`region_id` = `regions`.`id`
LEFT JOIN `first_aid_bookings`
ON `first_aid_courses`.`id` =
`first_aid_bookings`.`first_aid_course_id`
LEFT JOIN `first_aid_attendees`
ON `first_aid_bookings`.`id` =
`first_aid_attendees`.`first_aid_booking_id`
WHERE ( `first_aid_courses`.`location` LIKE '%$search_string%'
OR `first_aid_courses`.`venue` LIKE '%$search_string%' )
AND `first_aid_courses`.`deleted` = 0
AND ( `first_aid_bookings`.`cancelled` = 0
AND `first_aid_bookings`.`confirmed` = 1 )
GROUP BY `first_aid_courses`.`id`
ORDER BY `course_date` ASC
关于mysql - 快速复杂的查询来选择预订,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4038041/