Question

我有4张桌子：

学生 with over 7000 records
教师 with over 600 records
大学 with over 30 records
Lessons_Meta with over 10000 records

表学生列：

id | student_number | name

表教师列：

id | teacher_number | name

表大学列：

id | name

表 Lessons_Meta 列：

id | lesson_code | lesson_name | student_id | teacher_id | university_id

我的观点是：

CREATE VIEW `view_lessons` AS
SELECT
        *,
        (SELECT `name` FROM `students` WHERE `students`.`id` = `lessons_meta`.`student_id` LIMIT 1) AS "student_name",
        (SELECT `name` FROM `teachers` WHERE `teachers`.`id` = `lessons_meta`.`teacher_id` LIMIT 1) AS "teacher_name",
        (SELECT `name` FROM `universities` WHERE `universities`.`id` = `lessons_meta`.`university_id` LIMIT 1) AS "university_name"
FROM `lessons_meta`

我的查询是：

SELECT * FROM `view_lessons` LIMIT 20

20秒后，显示此查询已完成！如何减少这个时间负荷？

Answer 1

将您的视图更改为此

CREATE VIEW `view_lessons` AS
SELECT L.*,  S.`name` AS student_name, T.`name` AS teacher_name, U.`name` AS university_name
FROM `lessons_meta` L
INNER JOIN `students` S ON S.`id` = L.`student_id`
INNER JOIN `teachers` T ON T.`id` = L.`teacher_id` 
INNER JOIN `universities` U ON U.`id` = L.`university_id`

在lessons_meta表格中，在student_id，teacher_id，university_id
在所有表格上，确保id列已正确编入索引，通常它们应该是唯一的/ PK

MySQL - 我的视图很慢

1 个答案: