如何使用內部連接和子查詢優化SQL查詢和返回計數

Question

我們獲得的結果是正確的，但它需要太多的時間來執行。我們可以優化查詢，這將花費更少的時間來執行。

SELECT c.client_id 
FROM client_master c 
INNER JOIN user_visit_record u ON u.client_id = c.client_id 
WHERE c.dept_id ='1' 
    AND c.branch_id='1' 
    AND c.client_status IN('Hot','Warm','Cold','Quotation') 
    AND u.next_followup_date < '2017-06-01' 
    AND u.visit_id IN 
    (SELECT max(visit_id) 
    FROM user_visit_record 
    WHERE client_id=c.client_id) 

在此先感謝。

Answer 1

我已經使用*查詢，你能做的就是隻選擇需要的列，單程優化

和MySQL有一些現有的解決方案，檢查此Article

SELECT c.client_id 
    FROM 
     (SELECT * 
     FROM client_master 
     WHERE dept_id ='1' 
       AND branch_id='1' 
       AND IN('Hot','Warm','Cold','Quotation')) AS c 
    INNER JOIN 
     (SELECT * 
     FROM user_visit_record 
     WHERE next_followup_date < '2017-06-01' 
       AND visit_id IN 
      (SELECT max(visit_id) 
      FROM user_visit_record 
      WHERE client_id=c.client_id)) AS u 
      ON u.client_id = c.client_id 

Answer 2

這裏是優化查詢：

SELECT c.client_id 
FROM client_master c 
JOIN (SELECT * FROM user_visit_record u ORDER BY u.visit_id DESC) AS t ON t.client_id = c.client_id 
WHERE c.dept_id ='1' 
AND c.branch_id='1' 
AND c.client_status IN('Hot','Warm','Cold','Quotation') 
AND t.next_followup_date < '2017-06-01' 
GROUP BY t.clientid 

Answer 3

試試這個：

SELECT client_id FROM 
    (
    SELECT client_id 
     FROM client_master 
     WHERE dept_id ='1' AND branch_id='1' AND client_status IN('Hot','Warm','Cold','Quotation') 
) AS c 

    NATURAL JOIN 

    (
    SELECT client_id 
     FROM user_visit_record 
     INNER JOIN (
      SELECT client_id, max(visit_id) as max_visit 
      FROM user_visit_record 
       GROUP BY client_id 
     ) AS max_user_visit 
      ON (user_visit_record.client_id = max_user_visit.client_id) 
       AND (user_visit_record.visit_id = max_visit) 
     WHERE next_followup_date < '2017-06-01' 
) AS u