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sql優(yōu)化實(shí)戰(zhàn) 把full join改為left join +union all(從5分鐘降為10秒)

 更新時(shí)間:2020年09月19日 16:36:31   作者:陽泉酒家小當(dāng)家  
因?yàn)樘厥庠?,無法訪問客戶的服務(wù)器,沒辦法查看sql的執(zhí)行計(jì)劃、沒辦法知道表中的索引情況,所以,嘗試從語句的改寫上來優(yōu)化

今天收到一個(gè)需求,要改寫一個(gè)報(bào)表的邏輯,當(dāng)改完之后,再次運(yùn)行,發(fā)現(xiàn)運(yùn)行超時(shí)。

因?yàn)樘厥庠?,無法訪問客戶的服務(wù)器,沒辦法查看sql的執(zhí)行計(jì)劃、沒辦法知道表中的索引情況,所以,嘗試從語句的改寫上來優(yōu)化。

一、原始語句如下:

select isnull(vv.customer_id,v.customer_id) as customer_id,
		isnull(vv.business_date,replace(v.business_date,'-','')) as business_date,
		v.prod_id,
		v.sales,
		vv.visit_count,
    v.all_sales
from 
(
  SELECT a.customer_id ,
	    max(month)+'-01' as business_date,
      a.PROD_ID ,
      SUM(CAST(VALUE AS NUMERIC(38, 3))) sales,
      sum(SUM(CAST(VALUE AS NUMERIC(38, 3)))) over(partition by a.customer_id) as all_sales
							
  FROM  TB_IMPORT_SALES a 
  WHERE  a.customer_id IS NOT NULL
      AND a.PROD_ID IS NOT NULL
			and a.month='2016-11'
  GROUP BY a.customer_id ,
      a.PROD_ID
)v
full join
(
  SELECT customer_id, 
	    max(a.business_date) as business_date,
      COUNT(*) AS VISIT_COUNT 
	FROM TB_CALL_STORE a WITH(NOLOCK)
	inner join TB_TIME d
	on a.business_date = d.t_date 
	where d.section ='2016-11'
	GROUP BY customer_id
)vv
on v.customer_id = vv.customer_id

原來是left join,雖然查詢比較慢,但是2分鐘能查出來,現(xiàn)在按照業(yè)務(wù)要求,需要看到所有數(shù)據(jù),所以改成了full join,改了之后5分鐘都查不出結(jié)果。

二、改寫后的代碼

select v.customer_id,
		replace(max(v.business_date),'-','') as business_date,
		v.prod_id,
		max(v.sales_volume) sales_volume ,
		max(v.visit_count) visit_count,
        max(v.all_sales_volume) all_sales_volume
from 
(
  SELECT a.customer_id ,
	    max(biz_month)+'-01' as business_date,
      a.PROD_ID ,
      SUM(CAST(VALUE1 AS NUMERIC(38, 8))) sales_volume,
      sum(SUM(CAST(VALUE1 AS NUMERIC(38, 8)))) over(partition by a.customer_id) as all_sales_volume,
			null as visit_count
							
  FROM  TB_IMPORT_SALES a 
  WHERE  a.customer_id IS NOT NULL
      AND a.PROD_ID IS NOT NULL
			and a.month='2016-11'
  GROUP BY a.customer_id ,
       a.PROD_ID
  union all
 
  SELECT customer_id, 
	    max(a.business_date) as business_date,
		  p.prod_id,
		  null,
		  null,
      COUNT(*) AS VISIT_COUNT 
	FROM TB_CALL_STORE a WITH(NOLOCK)
	cross apply
	(
		select top 1 prod_id from TB_PRODUCT with(nolock)
	)p
	inner join TB_TIME d
	on a.business_date = d.t_date 
	where d.section ='2016-11'
	GROUP BY customer_id,p.prod_id
)v
group by v.customer_id,
     v.prod_id

由于代碼本身比較簡單,沒辦法再進(jìn)一步簡化,而由于連接不了服務(wù)器,其他的方法也用不上,甚至沒辦法分析到底是什么導(dǎo)致運(yùn)行這么慢。

想了想,full join 本質(zhì)上就是 2次left join+union ,無非就是合并數(shù)據(jù),于是嘗試一下用union all來直接合并數(shù)據(jù),現(xiàn)在改成unoin all最后,就不需要full join。

但是考慮到第2段代碼中并沒有prod_id這個(gè)字段,所以這里在第2段代碼加上了cross apply隨便取出一個(gè)產(chǎn)品的id,這樣就有prod_id這個(gè)字段,可以合并了。

修改之后,果然速度降到了10多秒。

到此這篇關(guān)于sql優(yōu)化實(shí)戰(zhàn) 把full join改為left join +union all(從5分鐘降為10秒)的文章就介紹到這了,更多相關(guān)left join +union all內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家!

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