mysql查询优化左连接

Question

我使用以下mysql查询来获取一些所需的结果，但问题是它需要更多的时间。 目前这个查询的执行时间是7456毫秒，这对我的项目是不可接受的，我想优化这个查询的任何想法？

 SELECT *, DATEDIFF(NOW(),ticketstatus_tbl.updation_date) AS problem_age,images_tbl.image_path
            FROM ticketstatus_tbl 
            LEFT JOIN question_tbl ON ticketstatus_tbl.question_id = question_tbl.question_id 
            LEFT JOIN ticketing_tbl ON ticketstatus_tbl.related_ticket_id = ticketing_tbl.ticket_id
            LEFT JOIN department_tbl ON question_tbl.question_dept = department_tbl.department_id
            LEFT JOIN branch_tbl ON ticketstatus_tbl.branch_id = branch_tbl.id
            LEFT JOIN images_tbl ON images_tbl.question_id = ticketstatus_tbl.question_id and images_tbl.branch_id = ticketstatus_tbl.branch_id
            WHERE (ticketstatus_tbl.ticket_status NOT IN ('Close')
            AND question_tbl.is_active_question = 1
            AND ticketstatus_tbl.display_status = '1'
            AND ticketstatus_tbl.flag_color = 'Yellow'
            AND department_tbl.department_name = 'Admin')order by ticket_number ASC LIMIT 0 ,5

谢谢

Answer 1

首先，您不需要所有left outer join ，因为您的where子句正在撤消其中的大部分连接。 我的猜测是所有可以变成内连接，但至少：

SELECT *, DATEDIFF(NOW(),ticketstatus_tbl.updation_date) AS problem_age,images_tbl.image_path
FROM ticketstatus_tbl 
            JOIN question_tbl ON ticketstatus_tbl.question_id = question_tbl.question_id 
            LEFT JOIN ticketing_tbl ON ticketstatus_tbl.related_ticket_id = ticketing_tbl.ticket_id
            JOIN department_tbl ON question_tbl.question_dept = department_tbl.department_id
            LEFT JOIN branch_tbl ON ticketstatus_tbl.branch_id = branch_tbl.id
            LEFT JOIN images_tbl ON images_tbl.question_id = ticketstatus_tbl.question_id and images_tbl.branch_id = ticketstatus_tbl.branch_id
WHERE ticketstatus_tbl.ticket_status NOT IN ('Close')
            AND question_tbl.is_active_question = 1
            AND ticketstatus_tbl.display_status = '1'
            AND ticketstatus_tbl.flag_color = 'Yellow'
            AND department_tbl.department_name = 'Admin'
order by ticket_number ASC LIMIT 0 ,5;

其次，您正在对ticketstatus_tbl进行过滤。 你应该在ticketstatus_tbl(display_status, flag_color, ticket_status, question_id)上有一个综合索引ticketstatus_tbl(display_status, flag_color, ticket_status, question_id) 。 如果可以，请将ticket_status not in ('Close')更改为肯定声明： ticket_status in ( Open , 'In Progress', . . .) 。 这使得索引更容易使用。

这是一个开始。