left join f3cim.f3cim_cfg_cust_rule cc on case when lot_hs.customer_id = 'WXM' THEN 'WII' || SUBSTR(lot_hs.mainpd_id, 6, 1) else lot_hs.customer_id end = cc.cust_id

这是一个 SQL 查询语句中的左连接操作，将表 lot_hs 和表 f3cim_cfg_cust_rule 进行关联。在连接条件中，使用 case when 语句对 lot_hs 表中的 customer_id 进行判断，如果等于 'WXM'，则将其替换为 'WII' + mainpd_id 字段中的第六个字符，并与 f3cim_cfg_cust_rule 表中的 cust_id 字段进行匹配。如果不等于 'WXM'，则直接与 f3cim_cfg_cust_rule 表中的 cust_id 字段进行匹配。左连接操作可以保留 lot_hs 表中所有记录，即使在 f3cim_cfg_cust_rule 表中没有匹配的记录，也会在结果集中显示。

相关问题

select lot_hs.lot_id as lot_id,lot_type,lot_hs.mainpd_id, created_time,COMPLETE_TIME, value(bank.banktime,0) as banktime , round ( ( 1.00*(days(COMPLETE_TIME)-days(created_time)) + (hour(COMPLETE_TIME)-hour(created_time))*1.00/24 + (minute(COMPLETE_TIME)-minute(created_time))*1.00/24/60 + (second(COMPLETE_TIME)-second(created_time))1.00/24/60/60) - value(bank.banktime,0),3) as use_days, customer_id, coalesce(cc.cust_id_define,lot_hs.customer_id) as cust_id2, cc.cycletime_target as ct_target, date,layer, round(count() over(partition by coalesce(cc.cust_id_define,lot_hs.customer_id),cc.cycletime_target)*0.9,0) cnt, row_number() over(partition by coalesce(cc.cust_id_define,lot_hs.customer_id),cc.cycletime_target order by ( ( days(COMPLETE_TIME)-days(created_time) + (hour(COMPLETE_TIME)-hour(created_time))*1.00/24 + (minute(COMPLETE_TIME)-minute(created_time))*1.00/24/60 + (second(COMPLETE_TIME)-second(created_time))*1.00/24/60/60) - value(bank.banktime,0))/layer) id From (select date(a.claim_time) as date, a.lot_id, a.lot_type,a.mainpd_id,a.prodspec_id,a.custprod_id, case when(date(b.created_time) <= '2009-01-05') then b.created_time + 21 days else b.created_time end as created_time, CASE WHEN A.CUST_id in ('MCA','NPA','SET') THEN a.COMPLETE_TIME ELSE a.COMPLETE_TIME END COMPLETE_TIME, a.cust_id as customer_id, a.ope_category, c.layer From f3rpt.F3_TB_DAILY_FABOUT a, f3rpt.fvlot b, (select mainpd_id, sum(masks)layer from f3rpt.ASMCRPT_VW_MAINPD_MASKS_ALL group by mainpd_id) as c, (select * from (select lot_id, max(claim_time)claim_time, count(case when(ope_category='Ship')then lot_id else null end) as LS, count(case when(ope_category='Unship') then lot_id else null end) as LUS from f3rpt.F3_TB_DAILY_FABOUT where substr(lot_id,1,2) not in('CA','CW','ES','E0','EM') and lot_type = 'Production' AND LOT_ID NOT LIKE 'H%' and substr(lot_id,7,4)='.00F' and ope_category in ('Ship','Unship') and year(claim_time) = year(current date - 1 days) and month(claim_time) = month(current date - 1 days) group by lot_id) as a where LS - LUS > 0 ) as lot Where a.lot_id = b.lot_id and b.mainpd_id = c.mainpd_id and a.lot_id = lot.LOT_ID and a.claim_time = lot.claim_time and a.ope_category = 'Ship' and a.cust_id in ('SM','BOE','GSC','NPA','GTA') ) as lot_hs left outer join (select lot_id,max(bankin_time) banktime from f3rpt.asmc_dpm where bankin_time>0 group by lot_id) bank on (lot_hs.lot_id = bank.lot_id) left join f3cim.f3cim_cfg_cust_rule cc on case when lot_hs.customer_id='WXM' THEN 'WII'||SUBSTR(lot_hs.mainpd_id,6,1) else lot_hs.customer_id end = cc.cust_id and locate(cc.mainpd_id,lot_hs.mainpd_id)>0 and locate(cc.prodspec_id,lot_hs.prodspec_id)>0 and locate(cc.custprod_id_45,substr(lot_hs.custprod_id,3,3))>0 where lot_hs.ope_category = 'Ship' ；以上sql如何优化

这是一个比较复杂的 SQL 语句，可以从以下几个方面考虑进行优化：

1.使用 JOIN 替代子查询

可以使用 JOIN 语句替代子查询，可以提高查询效率。例如，将以下子查询：

(select mainpd_id, sum(masks)layer from f3rpt.ASMCRPT_VW_MAINPD_MASKS_ALL group by mainpd_id) as c

改写为：

FROM f3rpt.ASMCRPT_VW_MAINPD_MASKS_ALL c GROUP BY mainpd_id

2.使用索引

对于频繁查询的字段，可以添加索引以提高查询效率。例如，可以为以下字段添加索引：

b.mainpd_id
a.lot_id
a.cust_id
lot_hs.customer_id
cc.cust_id_define
cc.mainpd_id
cc.prodspec_id
cc.custprod_id_45

3.使用 EXPLAIN 分析查询计划

使用 EXPLAIN 命令可以分析查询计划，了解查询语句的执行情况，从而优化查询语句以提高查询效率。

4.使用 UNION 替代多个 OR 条件

对于多个 OR 条件的查询语句，可以使用 UNION 来代替，可以提高查询效率。例如：

AND lot_type = 'Production' AND LOT_ID NOT LIKE 'H%' and substr(lot_id,7,4)='.00F' and ope_category in ('Ship','Unship')

可以改写为：

AND lot_type = 'Production' AND LOT_ID NOT LIKE 'H%' and substr(lot_id,7,4)='.00F' and ope_category = 'Ship'
UNION
AND lot_type = 'Production' AND LOT_ID NOT LIKE 'H%' and substr(lot_id,7,4)='.00F' and ope_category = 'Unship'