具有多个左连接的mysql查询需要大量时间来获取数据

Question

我正在使用 mysql 选择查询从多个表中获取行以生成报告。

随着行数的增加，获取需要花费大量时间。

我发现使用左连接会使查询变慢。

可以使用什么替代方法使查询执行得更快。

下面是我正在使用的查询。查询的结果是根据患者年龄和疾病类型给出患者数量的报告。

例如：疾病是病毒性发烧，比当月 0 到 15 岁男性、0 到 15 女性、16 到 45 男性、16 到 45 女性之间的患者人数是多少。

查询：

    SELECT 
        ds.disease_type as disease, 
        SUM(CASE WHEN (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' THEN 1 ELSE 0 END) as patient_count, 
        SUM(CASE WHEN ((DATE_FORMAT(pdm.visited_date, '%Y-%m-%d')) BETWEEN '2019-04-01' AND '2020-03-01') THEN 1 else 0 end) as disease_morbidity_cumulative_no,
        SUM(case when ic.age BETWEEN 0 AND 15 AND ic.gender ='male' AND (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' then 1 else 0 end) as patient_age_count1_male, 
        SUM(case when ic.age BETWEEN 0 AND 15 AND ic.gender ='female' AND (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' then 1 else 0 end) as patient_age_count1_female, 
        SUM(case when ic.age BETWEEN 16 AND 45 AND ic.gender ='male' AND (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' then 1 else 0 end) as patient_age_count2_male, 
        SUM(case when ic.age BETWEEN 16 AND 45 AND ic.gender ='female' AND (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' then 1 else 0 end) as patient_age_count2_female, 
        SUM(case when ic.age >45 AND ic.gender='male' AND (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' then 1 else 0 end) as patient_age_count3_male, 
        SUM(case when ic.age >45 AND ic.gender='female' AND (DATE_FORMAT(pdm.visited_date, '%m-%Y'))='10-2019' then 1 else 0 end) as patient_age_count3_female 
    FROM (p_d_m pdm) 
        LEFT JOIN i_card ic ON ic.i_card_id = pdm.i_card_id
        LEFT JOIN disease ds ON ds.disease_id = pdm.disease_id 
        LEFT JOIN village v ON v.village_id = ic.village_id 
        LEFT JOIN phc p ON p.phc_id = v.phc_id 
        LEFT JOIN ind_card indc ON indc.ind_card_id = pdm.ind_card_id 
        LEFT JOIN block b ON b.block_id = p.block_id 
        LEFT JOIN sub_district s ON s.sub_district_id =b.sub_district_id 
        LEFT JOIN district d ON d.district_id = s.district_id 
    GROUP BY ds.disease_id

我可以通过什么方式更改查询，以便我可以使用所有连接并且不需要太多时间。

Answer 1

为什么你不把查询结果放在数据库视图中然后从创建的视图中选择 *