mysql查詢優化左連接

Question

我使用以下mysql查詢來獲取一些期望的結果，但問題是它需要更多時間。目前這個查詢的執行時間是7456毫秒這是我的項目無法接受的，我想優化這個查詢任何想法？

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 

感謝

Answer 1

首先，你並不需要所有的left outer join，因爲你的where子句撤銷其中的大多數。我的猜測是所有可以變成內部連接，但在最低限度：

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，你正在做的ticketstatus_tbl過濾。你應該在ticketstatus_tbl(display_status, flag_color, ticket_status, question_id)上有一個複合索引。如果可以，請將ticket_status not in ('Close')更改爲肯定性聲明：ticket_status in (打開, 'In Progress', . . .)。這使得索引更容易使用。

這是一個開始。