需要關於加速查詢的建議

Question

該查詢大約需要9秒鐘並返回2條記錄。

SELECT 

s.description, s.improvement, 
s.first_name, s.last_name, s.finding, s.action, s.share, 
s.learned, s.timestamp, d.title as department_title, 
group_concat(DISTINCT g.title SEPARATOR " | ") as strategic_goals, 
group_concat(DISTINCT m.statement SEPARATOR " | ") as mission_references, 
group_concat(DISTINCT meas.statement SEPARATOR " | ") as measure_statement, 
group_concat(DISTINCT o.statement SEPARATOR " | ") as outcome_statement, 
group_concat(DISTINCT i.title SEPARATOR " | ") as ilo_title, 
group_concat(DISTINCT cv.title SEPARATOR " | ") as core_value_title, 
y1.year as current_year_title, y2.year as previous_year_title, 
u.file_name as file_name 

FROM summary s 

LEFT JOIN year y1 ON s.current_year_id = y1.id 
INNER JOIN year y2 ON s.previous_year_id = y2.id 

INNER JOIN strategic_goal_entries sge ON s.id = sge.summary_id 
INNER JOIN goal g ON sge.goal_id = g.id 

INNER JOIN outcome o ON s.id = o.summary_id 
LEFT JOIN measure meas ON o.id = meas.outcome_id 

INNER JOIN department d ON s.department_id = d.id 
LEFT JOIN uploads u ON s.id = u.summary_id 

INNER JOIN mission_entries me ON s.id = me.summary_id 
LEFT JOIN mission m ON me.mission_id = m.id 

LEFT JOIN ilo_entries ie ON s.id = ie.summary_id 
LEFT JOIN ilo i ON ie.ilo_id = i.id 

INNER JOIN core_value_entries cve ON s.id = cve.summary_id 
INNER JOIN core_value cv ON cve.core_value_id = cv.id 

INNER JOIN executive_of_department eod ON s.department_id = eod.department_id 

WHERE eod.executive_id = 3 

GROUP BY s.id 

我添加了其餘的主鍵。查詢從9秒變爲2秒。

然後我設置引用其他表的主鍵的字段作爲索引字段。查詢從2秒到20秒，我是否分配了太多索引？

有什麼方法可以加快速度？

Answer 1

1.設置索引等後，通過限制JOIN條件可以加快一點。例如，而不是

LEFT JOIN uploads u ON s.id = u.summary_i 

做

LEFT JOIN uploads u ON (s.id = u.summary_i AND s.id = 3) 

的WHERE子句評估畢竟表都已加入。儘可能準確地預測您的JOIN條件。

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2.你嘗試從您的選擇構建視圖和執行SELECT * FROM myView WHERE myView.id = 3？

更新：閱讀this blog comment。